Subwoofer for two channel system

I love my stereo system. It includes the following:

Rowland Synergi IIi preamp
Rowland M201 amps
Cal Audio Labs CL-10 multi disk
Meridian 588 CD player
B & W N802 speakers
Reimyo DAP-777 DAC

I am very interested in adding one or a pair of subwoofers to the system but I do not want to mess with the sound too much. Just add a bit bass to make it perfect. Any suggestions would be greatly appreciated.
The VBT (aka TBI) Magellan VIII is another good option that meets your criteria. Very tuneful bass that doesn't get in the way, and has a small visual impact.
I'd recommend a pair if you can swing it, and place them in the corners. I believe they have powered ones but I used a separate bass amp (with my Tact crossover).
I eventually replaced them with RBH subs (also very good, but fairly imposing visually) because I wanted to move more air and set the crossover higher. The VBTs however, were a bit quicker and more tuneful.
IMHO, stereo subs is the way to go, with a separate amp using speaker level inputs (an amp vibrating in a sub box--not a great idea).
I'm beginning to sound like a broken record, I know, but you really do owe it to yourself to check out the Digital Drive series from Velodyne. Amazing subs!

I was going down this path at one point, but decided against it. Subwoofer integration is *very* difficult from talking to two people I've spoken to.

A friend of mine has the TacT 2.2 and he's integrated a Rel into his Sonus Faber Signum setup. The TacT will give you significant control for the integration. He's happy with his integration, but he's come a long way from just simply adding a subwoofer.

Another friend I know actually builds speakers and is *very* technically saavy with designing his own crossevers. After a very long and technical discussion, I came away with the concept of woofer speed differences; in order to come close to a 'good integration' the woofers of both speaker systems (the satellite and sub) should be within range of each other. For example, I was discussing my setup and what would be a good starting point - I have a D'appolito layout for my main speakers with 2 6" drivers for the midbass. To get a proper subwoofer to match the speed of my main speakers, I would want to go with the same size drivers for the subs. Which lead me down to the VBT line of subs. I remember going to the HE2004 show this past summer to hear the VBT, and I did not like what I heard, but then again, it was a hotel room where acoustics are terrible.

I was out in a high end store in the Bay Area and my girlfirend and I listened to a pair of Avalon speakers (can't remember the model, but it was their top end with diamond tweeters) and the system had the top end Rel sub in the system. The bass was not coherent at all, and this was a fully optimized system for the listening room. Both my girlfriend and I thought the system sounded much much better with the sub turned off. The sales guy thought we were crazy, but keep in mind, they just want to sell you gear.

I guess what I'm trying to say is, you're probably better off upgrading to a speaker with more range than adding a sub to a pair of bookshelf speakers. From what I see, you've invested a significant amount into your system. Why not do it the right way and look for a floor stander rather than add a sub to a pair of bookshelf speakers?

But if you're sold on going the sub path, Richards above has the right idea. VBT is probably the best place to start, keeping in mind you'll have to get an amp and active xover to driver the subs. Any other sub with an amp built in is really 'mid-fi' at best.
James the speakers are Nautalis 802s. They are floorstanding speakers with two 8" woofers. Your comments are very interesting though. Do you still have the same opinion that my speakers are the weak link? I know a lot of audiophiles really look down on B&W but I have auditioned many a speaker and these have the detail and seet sound that I like.
Hi Bryan,

only subwoofered system i've heard which is/was coherent and having rhythm and attack is based on TACT's RCS 2.2x and their dedicated subwoofers. These subwoofers are specially made for integration with TACT's pre.
This system, - all TACT gear (cd drive i do not remember), speakers was Dalis latest Euphonia MS 4.
(I think TACT are in the process of changing/renewing the speaker and sub lineup as i write this post.)
I promise You, adding a subwoofer will be Your biggest regret ever if not with the TACT's pre and subwoofers!
I had the REL - Stentor through 4 apartments..never ever did i get it to integrate seamless!
Still we tried every setup endlessly!
Coherent- no way! Not even the sales guy could say otherwise!
It's simply to much which seem to become a problem,
not just the bass!
I suggest You contact a speakermanufacturer to get proper info concerning the tech talk and so on.
Do Yourself a favour, do what ever You could to "demo"
the Krell FPB 600C or 700CX.
The 600C and 650MC's was used as power amps when the Nautilus was voiced.
What other amp give You that crystal-clear transparency, bass drive and impact at the same time???
I think your preamp will work super in this combo!
I ended up buying a Krell FPB 600C. I had solved the problem with above complaints!
You will get more attack and drive from Your speakers if You add a amp with more power reserves!
Beef up the soundstage and the impact. The control is at a different level.
Maybe that is what You search?