Anyone Successfully Go from Floor Standers to Bookshelf Monitors w/ Subs?

My system is in a Large Living room which opens to dining room & Kitchen. I figure about 6k cu ft. I have Silverline Sonata speakers now with subs. Unfortunately I did not build my addition when I should have 10-15 yrs ago. Now I'm not really up to the task. Too old & wore out. So I'd love to make the LR a prettier room for my wife. One thing we talked about was the large speakers, and possibly using Watkins Gen 4 monitors. But as good as they sound, I am concerned about the ability to fill the room, or at least my listening area. As I understand, it is about moving air. I cannot see how a 6.5 & 1 inch speaker can move as much as a 10, 7, 3 & 1 inch. So I am quite concerned about that. Right now, the system sounds very pleasing to both of us. We don't want to take a backward step but can live with a sideways step if it is more visually pleasing.

Has anyone made this kind of a step from floor standers to monitors, both with subs, in a large room, with success? Or am I thinking correctly about the small speakers inability to move the proper amount of air for the room size? Thanks for your help.

OH, FWIW, The addition may not be completely out of the picture. But it depends on whether I can get one of my previous sub contractors to do a large part of it. 
Went there...   no substitute for larger drivers, went back to floorstanders.  
Here's an article I wrote on this matter. The short answer is, if you must go with subs get an integrated or pre with built in room correction and automatic bass management.
In our former home, I moved my system with two excellent Totem Fire monitors and a Velodyne 10" powered subwoofer down from our 13x22' living room to our 24x26' family room and the system just didn't seem to fill the new space.

That gave me an "excuse" to upgrade all the components in my system!  :-)
You're looking at the wrong monitors. You're right a 1in and 6.5in won't compete without a subwoofer. Instead look at a 1in tweeter - 8in mid - 8in X 2. Woofer.
Thats much more than a speaker, it's a system.   How much for everything  needed turn key?
Maybe go with smaller and attractive floorstanders that punch above their weight?  Also obviously avoids the hassle of integrating subs.  Something like the Joseph Audio Perspective 2 might pass the WAF and size test and still fill your room adequately.  I also suspect they’ll have the same sonic qualities you like about your excellent Sonatas.  Best of luck. 
Thanks for the answers so far. FWIW, I have 2 Sumiko S10 subs which are a clone of the Rel S5. they have Fiberglass Cones instead of metal (I believe that is correct). The speaker size and amps are the same size 12" & power 550 watts as well as their connection types. They are very easy to integrate and work well with my speakers now. I agree with Eric, in that integration is extremely important. 
I've also considered the Silverline Prelude Plus which are thin towers with 4 3 1/2" woofers/mids & soft dome tweeter. Supposedly go to 35hz. Yeah, mine were supposed to do 20hz. Also I have heard the Gen 4's and they are quite amazing for monitors. Bill Watkins was a master of bass who holds several patents including for the  Infinity-Watkins Dual Drive Woofers . The Gen 4's go to 41hz with great clarity. But again, the amount of air pushed is questionable
I have really been wanting to audition the Larsen 6 and 8 speakers. They can be (and are designed to) placed up against the front wall, have great bass, and throw up a wall of sound that sounds like a "live" performance, reviewers say. They are very room-friendly.

<< I felt it was important to drive the 6.2s with an amplifier priced more in line with the Larsens, and so I connected them to a $995 Parasound Halo A23. While there was some loss of tonal refinement and detail with the switch, the bass definitely improved. The Parasound puts out 200Wpc into 8 ohms as opposed to 60Wpc for the Passes. Clearly, these little speakers thrive on power; in fact, I later learned that John Larsen’s reference amplifier is a Gamut Di150 LE, which is rated at 180Wpc into 8 ohms. I then did something I wasn’t originally planning on doing—powering the 6.2s with my 200Wpc David Berning Quadrature Z monoblocks, an undeniably unlikely pairing as these amps cost roughly eight times the price of the speakers. The sonic result was amazing, including the bottom end. Bass and kick-drum had satisfying punch, and the organ in the Philadelphia Orchestra’s recording of the Saint-Saëns Symphony No. 3 on an Ondine SACD was majestically massive. Like many well-designed loudspeakers, the Larsen 6.2s will perform well with modestly priced amplification of high quality but also have the potential to sound even better with über-electronics.

The other opportunity to improve bass performance came when I ran a DSP room-correction calibration with the Anthem’s ARC software. Inspection of the frequency response curves revealed some irregularities from around 30 to 400Hz—a phenomenon I’ve noted with most loudspeakers I’ve measured in this fashion. Employing the calculated room correction helped to smooth out the bass response considerably, on paper and to my ears. The lesson is this: The up-against-the-wall placement of Larsen loudspeakers offers a definite advantage in terms of bass output compared to free-standing speakers in a typical domestic environment. But that doesn’t preclude room-related irregularities in bass response that may require attention with either physical acoustical treatments or electronic room correction.

For its size, the Larsen 6.2 is a definite overachiever when it comes to bass output and dynamics that won’t leave most listeners uninvolved—whether with late-Romantic symphonic repertoire or energetic pop and rock. If you’re going for realistic dB levels with Boris Godunov or Daft Punk, you’re going to be disappointed. For many, though, the 6.2s will effectively transmit the power and excitement of large-scale music of all sorts because of all the things it does so well. What we have in the Larsen 6.2 and other Larsen models is the full realization of a decades-long effort to understand the behavior of real rooms and to leverage those observations in the design of a loudspeaker that will play music with a minimum of coloration and distortion. If your loudspeaker budget is anything up to $5k, the Larsen 6.2 deserves a very, very long listen.>>

I've successfully gone from floor standards to the Fritz Carbon 7 SE mkii and and much more pleased with the more accurate, tight base in my 18 x 15 room then I ever have been with floor standers.
Dear @artemus_5 : Normally you don’t need to worry about the monitors can fulfill your room because will does it even more than enough.

You have rigth now a " big " true problem with your Sonata speakers. Yes I know that you like it but this " you like it " just does not helps to disappears the problem.

Problem name is IMD ( InterModulationDistortion. ) high levels ( that you are accustom to. ) and THD too and the problem comes because the manufacturer designer choosed as crossover frequency 1.5khz and this means that that driver/woofer handled frequencies as low as 25hz all the way over 1.5khz.

We don’t add a paiir of self powered true subwoofers to achieve lower bass levels, this is an advantage to integrates subs but the main issue is to lower the IMD/THD of your room/system and this always will has a rewards because you will listening better quality performance levels with a lot lower distortion levels.

Here you can read the why of my take about:

You can do it with your today Sonatas crossing two a pair of TRUE self powered subwoofers that today normally comes with an integrated software and microphone to make the rigth system integration.

Or you can do it two with these excellent monitors:

That’s why I posted to the gentleman that asked for the Wilson Alexx V one alternative with monitors/subs that with any single doubt will outperforms any full range passive speakers.
Unfortunatelly the overall knowledge levels on the specific issue is lower than what we think and not even " professionals " reviewers as M.fremer has it when for years is using full range Wilson speakers. Yes he is wrong when does it and the overall full range speaker owners could achieve good rewards if just think/learn how to outperforms what they have rigth know with a really small investment on monitors/subs alternative. That gentleman on the Wilson V instead to ask for a better alternative just wants to follows behind what he is accustom too even if it’s not the best path for him.

High Quality room/system levels is not about just money but mainly about knowledge levels.

Regards and enjoy the MUSIC NOT DISTORTIONS,

The short answer is yes. The helpful answer is probably much more complex.

If you want to use a monitor you will want to design the system so the subs do the heavy lifting. IOW the higher the crossover point the better. 

Your concern about a 6.5” woofer being able fill that large of space is legit. Speaker makers can design a very small box and cone to cycle quite low but I have yet to hear one do it at realistic volume levels.

In my opinion, depending on what types of music you listen to and how loud you listen to them, I would cross the subs at no lower than 80 Hz and preferably closer to 120 Hz and if you really like it loud probably higher than that.

Dear @audiorusty @artemus_5  : I forgot that crossover frequency that's so critical and my take is to have the frequency crossover around 80hz-100hz.
In this way the monitors or today speakers will run/handled frequencies from 80hz-100hz and all the way up to its hig frequency limit.

Spendor or ProAc mini monitors with a couple of 10–12” servo-controlled Velodyne subwoofers should work a treat. 
I went from Salk Song3's (standard version w/bamboo midrange) to a pair of Clearwave Duet 6 monitors and a pair of REL T5i subs. First, both systems sounded great but there were tradeoffs probably because the speakers are different. The Clearwave's use accuton ceramic drivers vs the RAAL/bamboo/paper drivers in the Salk. With the Clearwaves and RELs the bass was more detailed, tighter, more accurate. I preferred the RAAL in the Salks to the ceramic tweeter but not by a huge margin. The RAAL just gets an airier presentation I prefer. Overall, I thought the Clearwave/REL system was more detailed, more accurate, and had better bass. However, I never tried the Salks with the pair of RELs, but I was pretty pleased with the Duet 6/REL combo and while I've moved on to Cube Nenuphars, I wasn't feeling like bringing the Salks back to replace the Duet 6/REL combo.
I have owned many floor standers ,a good monitors disappears better and images great . I mod all the Xovers in every loudspeakers I buy for even in $20k+ speakers and up many are 
not what I would consider great parts quality in their Xover which is the heart of all Loudspeakers.
i recently bought the very good Elac Vela 403 monitors with their latest gen -5 Jet AMT tweeter ,and Diamond sandwich Mid-bass,
very well thought out design and sounded very good even before Xover upgrades,and uses the excellent SVS  SB 3000 subwoofers with their excellent app. Loading the stands with sand ,lead shot 
makes a noticable improvement , and I had custom cut black granite tops  for monitors and subs which makes great mass loading for resonance absorption and increased imaging for  under $6k this setup competes very well with floorstanders 2x+ the cost.and does several things better.
Subs and monitors take up more room than just floor standers. 
I am of the option that subs integrate best with large speakers. The power band transition between the two is closer. 
I would just get some floor standers she likes the look of. Sonus faber is alway a hit with the wives. 
When you go from a large floorstander to a small bookshelf model you not only lose bass but you also lose image size and projection of the sound that is what a large baffle is for to better couple the drivers to the room and this very thing causes the sound and image to suffer.
   Moving air? What kind of bass do you prefer? Tooth rattling or well integrated or both? Bass is a personal preference. "Moving air" isn't the whole part of it. There will be scads of advice on this topic. The best sound and the physical appeal seems to be your goal. I have heard book standers with subs that out perform floor standers and others that do not.
   Speaker placement, especially with subs, is paramount. When I say subs that means more than one. Ask millercarbon about the swamp effect. Room correction, room treatments, and other tools can help to achieve a good sound. If you go the bookshelf path with subs be prepared to tune them to your room and your music tastes. Especially speaker placement if the room geometry allows. Here's an informative article on subs......

I went from large Axiom M80 floor standing speakers in my family room, to Focal 906 bookcase sized on stands. The Focals sounded much better and filled the room just as well.  They also visually were much more appealing to look at and my wife was happy with the look.  I opted for dual subs which lived at the back of the room (and for a time actually acted as rear stands for my surround speakers LOL). Very satisfying to listen to in a less than perfect room.

Then I moved to a new house and even though the family room was larger every wall was glass so no room for speakers of any kind ha ha. I went back to floor standers in my basement listening cave but only because I scored some on Craigslist that a guy didn’t know what he had for 100 bucks when they should’ve been 1000 or more. Vintage 90s floor standers but I still use the dual subs even with them.  I do miss the Focals however and keep my eye out for a used pair of 926 or 936 floor standers (which again would be much more visually appealing the older 80s and 90s speakers are not very attractive boxes for the most part). 
You might want to try the new gold 200 generation 5 or the platinum 200 generation 2 or maybe even the gold 300 generation 5.
I made the transition years ago, but and this is a big but, my monitors are the (almost) vintage Miller & Kreisel MPS-2510 professional studio monitors paired with (2) PSA (18") 1801’s subwoofers and this ensemble can handle anything I throw at them.

The subs were a breeze to integrate and the monitors with their (2) midrange and (3) tweeter vertical configuration have a wide dispersion soundstage and are MADE to and crossed over to be used with SUBS and NOT to be used as stand alone monitors only.

I will say this: The bigger the sub the better as I kept upgrading to bigger subs until I got it to SOUND right in my room for me. The unusual thing I find about the bigger subs is you don’t have to turn the gain up as much to integrate them vs using a smaller sub, which may sound counterintuitive.
You might want to try the monitor audio gold 200 generation 5 or the platinum 200 generation 2 or maybe even the gold 300 generation 5 very deep faster articulate base from all those speakers. And very three-dimensional and natural sounding as well, very big wide and deep sound stage.

If the Watkins Stereo Generation Four monitors are as good as the are reviewed here:

They may just work, but BEWARE of ’audiophile reviewers’. For the same price I’d go with the Tekton Impact Monitors, and they would blend in nicely with many a subwoofer.
I have and never look back. When done right with 3 to 4 subs, you will ask yourself why you didn’t think of it sooner.  The location requirements for bass drivers and everything else are very different. It makes sense to separate these two into subwoofers and stand mounted speakers. Then each challenge can be tackled separately and independently. You will need room correction software to integrate the two successfully but the results (visually and sonically) are to die for. 
My LR also opens to a large dining room, kitchen, and hallway.

i have 2 speaker systems. One is a pair of floor standing towers. The other is a quite small pair of bookshelf monitors I built 30 years ago, with a dome tweeter and 5-1/4” midwoofers. Both pair use the common Velodyne DLS subs.

The only difference is the sound character between the floorstanders and small bookshelf speakers. Both fill the space equally as well. 

But, I do have to change the crossover on the subs. 40 Hz for the floorstanding towers and 100 Hz for the bookshelf units. I have a remote control for the subs.

Sometimes I just like listening to my own designed and built speakers. For their size, I’d put them against ANY bookshelf speaker sold today.

As for SQ and filling the space, both are equal. 
@artemus_5 , I grew up in Kingsport, TN, and have been in and out of Watkins Stereo Center since 1978.  Bill Watkins makes incredible speakers -- always has.  His original WS-1A speakers are highly coveted and hard to find nowadays.  You will love the Generation 4 speakers, they sound incredible and have more bass than any Bookshelf Monitor speaker I've ever heard.

Watkins Stereo Center sold a popular Hi-Fi package in the late 1970's -- a Dual turntable, a Kenwood receiver, and a pair of WS-1A's.  If you were in high school with this setup at home, everyone knew where the Friday night after the football game kegger was taking place!
Sometimes you have to sacrifice in life, and moving from a fine floorstanding speaker to a fine bookshelf speaker with subs in a large room is going to be a downgrade imho. I sadly have had to make that exact move due to health issues and wife’s requests, and there simply aren’t any bookshelf speakers that can replace PSB Synchrony Ones. You’ll still enjoy the music, but you wont be sitting in the front row anymore. 
While I love Tower Speakers. I have a soft spot for a pair of good quality (north of $1k) Bookshelf Speakers on Stands with Dual Stereo Subwoofers. Integrated properly, they will disappear  into the room much easier IMHO.

Price is also another consideration.
I did but calling them monitors is hardly accurate.  Aerial LR5s with dual Aerial SW-12 subs.  The "monitors" are each 105 pounds with dual 9-inch woofers.  On their Signature Sound Anchor stands each speaker/stand weighs about 175 pounds.  The subs, also on SA stands, weigh 157 pounds each.  With enough power, the sound is dynamic, clean, and tonally rich.  
I replaced older KEF Reference 107/2s with newer KEF Reference 1s supplemented by a pair of Velodyne HGS-15s.  The sound was superb for smaller orchestrations, e.g., the jazz and baroque I prefer, but disappointing for large orchestrations until I raised the crossover from 40 to 80 Hz.  That transformed the setup, making the soundstage seem larger and deeper, and large orchestrations as enjoyable as they were with the 107/2s.  I use a SMS-1 bass manager that provides acoustic room correction, and plan to add a third HGS-15 diagonally across the room, behind the listening area. 
When I moved some years ago, I ended up with a smaller listening space. Found that my Vandersteen 2CEs just didn't work well in close quarters. They need room to breathe and that's something I didn't have. Ended up replacing them with Kef LS50s and a Rel T/5i sub. The LS50 coincident/coaxial driver design works very well in nearfield listening situations.   
There are many floor standing speakers that are quite thin and uses 8 + 6 inch drivers or many 8 inch drivers. One of those with a sub may be a good compromise. Could look good and fill enough of the room.

You can also listen to the Kii Three which moves a lot more air than you would think. But that would replace your amps as well.
Slightly off topic: Do you remember the double large Advent speaker setup? I have often wondered if that kind of synergy occurs with other monitor type speakers. Anyone here ever try that with today's high quality monitors (Watkins, Fritz, ProAc, Harbeth, etc)?
Wow! So many responses to answer. Thanks guys. FWIW, the Watkins Gen 4 have a return policy and Watkins Stereo is about 3 miles from my house. So, they wouldn’t be that hard to return. Once again, I have 2 Rel S5 subs (with Sumiko S-10 badges) So the subs are adequate for the job and I like them. I agree with @rauliruegas about the setup and crossover points. I have also played live music (drums & vocals) so I KNOW what a bass guitar should sound like and these subs do that well.

@allenf1963 We may be neighbors. I’ve lived in Kingsport for 25 yrs and have known Bill Watkins & his son for 35-40 yrs. I used to go up to just talk with Sr from time to time prior to his death. Bill Jr, says he was a genius and I believe it. I know about his patents & I believe he holds some on the Gen 4 too. Both speaker drivers are modified by Bill to get the desired outcome. He told me before he produced them that he was working on the best speaker he had ever produced. Again, Bill Jr says they are better than the WE-1’s. There again, Jr’s hearing is not as good as his fathers from what I understand (tinnitus) Nonetheless, both of them are very knowledgeable and are men of high integrity, IMO
Yes...for my second dedicated stereo room, which is small, I bot Tannoy Autograph mini and a Rel t7i paired w my old, but wonderful McCormick DNA-1...very happy with this second, intimate system.
I just set up a pair of the new Fleetwood Audio Deville Monitors. very big sounding speaker...>I’m not even sure if I need my sub with it. Here’s a quick video I made of is better than a picture.
There's no way to duplicate a big woofer playing mid and upper bass.  I've gone back and forth and the energy isn't there without a big woofer, 8" minimum.  The only way I've heard small woofer speakers rival big ones is nearfield.  This is a good way to go in my opinion and I'm surprised more people don't do it.  If you want your small speakers to rock put them a couple of feet away and they'll do a lot better than they do across the room.  
I have a small listening space. So I opted to go with SF Sonetto 1’s with the matching Gravis 1 subwoofer. Basically, It’s a Rel T5i with a down firing 8” woofer. Anyway, this combination works well in my room. The Sonettos’s are great at creating a good imaging sound stage and the Gravis 1 subwoofer helps the Sonetto speakers provide a good tight bass response that’s enjoyable to listen to. Granted, its not earth shattering or chest thumping bass.  But then again, I’ve never been a Bass Head.
NO!!!. Has anyone traded there very nice stereo equipment for a cheap shallow sound stereo. Really?
In my opinion you will likely be disappointed. I purchased a pair of Sonus Faber Cremona Auditor M's to replace my B&W DM6's as I thought I would be down sizing and they would be perfect in a smaller home. I loved the full size Cremona's however was told they needed a lot of room. The Auditors were beautiful to look at and the sound of voices were butter. They lacked bass though so after much investigation I purchased the suggested Rel Sub. Better though very hard to find the proper placement and unfortunately the mid bass could not be replicated I was used to with the B&W's. Luckily for me I bought both speakers and sub used and was able to re coup my expenditure on them. As I had not sold my B&W's I went about replacing caps (my brother in law gets the credit there) in the crossover and that upgraded the sound though I do miss the beautiful Auditors. Needless to say full sound of the floor standing trumped the beauties.
No difference at all if set up correctly with tweeters at ear level. There are very few floor standers that will go as low as good subwoofers so, given the choice I would go with stand monitors and subs. But, floor standers with sub could potentially be the same. I depends on the coloration of the speaker. Digital correction and subwoofer management is an excellent idea. All my friends that have heard my system all have eventually add digital correction to their systems and nobody is complaining. It makes getting subwoofers right so much easier.
Why not? I went from Daedalus Ulysses with a REL Stentor III sub to a pair of upgraded Buchardt S400 with the same sub. Smaller room required smaller speakers. 
I would suggest a pair of speakers that are designed to be put into the corners of the room. The Audio Note AN-E/LX HEMP might work for you. I realize that these are not bookshelf speakers nor would you need a subwoofer, but being that they are designed for corner placement your wife might accept that as an alternative. I know they will sound good in a larger room and they come in a lot of finish choices that should appeal to your wife,
The advantage with subs (depending on sub quality), is you can place the bass drivers where they perform best in your room, which is usually somewhere other than where the mid and treble speakers perform best.

Subs and monitors take more effort to dial-in, but, the results are often superior to floorstanders IME, especially when limited by a budget of a mere mortal.
The smaller stand mounted speakers I have heard do not seem to carry the same gravitas as larger floor standers.  My stand mounts have dual 9-inch woofers each crossed over at  360Hz to a 6-inch midrange and they do just fine down to about 40Hz where the dual subs take over.
One question for the group is whether there is a benefit to getting the woofers up higher away from the floor (i.e., stand mounted speakers vs. floor standers).  When I went from moderately large floor standers to my current stand mounted speakers, the bass cleaned up considerably, which seemed to add resolution throughout the entire frequency range, without sacrificing body or fullness.  The deep bass (below 45Hz) from the subs is also better controlled and cleaner, and probably deeper too, than what my previous ported floor standers provided.
I use ProAc D20R with a REL S/510 Room is 15x21 I have no issues with filling the room with music. I was considering ProAc D2R but with stands but the foot print is the same as the D20R’s
Yes, but & this is a big “but”- was second system, upgraded to used Harbeth 30 M, took a lot of time dialing in subs from “not there”, almost there, too much there, way too much there” & back, wouldn’t have worked for main system.
good luck!