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. 
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.