Best sub for Quad 988

I thoroughly enjoy my Quad 988 esl loudspeakers - extremely accurate reproduction of sound. The one thing I think I could improve on is the lack of bass dynamics.

Now I'm not talking about the sound of those annoying 'boom cars' or even the feel-my-shirt-ripple movie theater sound -- I'm talking about the accurate reproduction of drum dynamics you hear at a live music session (the instrument, not the amplification).

Thus, is there a sub that can reproduce acuate unbloated sound that can keep up with the Quad 988?
you may want to move the speakers around a bit in your room(back toward the rear wall maybe) before going the sub route. kick drum and other percussive stuff should sound more dynamic and have more weight, without giving up much transparancy.
The little TBI Magellan VIIIsu subs are amazing little beasts. One would probably work fine with your Quads, but a stereo pair is really the way to go. These are the fastest subs I have ever heard, better than the REL Stentor III I owned before. They are known to blend seamlessly with horns (a lot of people are using them with Avantgarde Duos) and electrostats. Should be perfect for the 988s.
My Quads are 3' from the rear wall and within inches of the side walls, toed inward about 6 degrees, and raised off the floor about 15" bolt-set (solid) to solid granite bases (garden statue bases - each one about 75lbs before I mounted the Quads) -- you think I the Quads should be further back Jaybo?

Markxii -- I have seen the TBI web site and have thought about a stereo pair, but have not been able to hear them or compare (no TBI dealers my way). How would you describe your sound? Also, I was reading the article in the new TAS (March 07) about the new Wilson-Benesch -- that intrigues me too.
The best way to describe the sound of TBIs is that you don't hear them at all. What I mean here is that there is simply no overhang, the notes stop as quickly as they begin, with excellent detail which is obscured and blended into one mush by most other subs. What these amazing little subs do is create the illusion that the main speakers are simply reaching lower - the integration is very seamless. The Rel Stentor was very similar, however I could hear a little bit of thickening and smearing, which I don't hear with the TBIs. The REL would be a better choice for larger rooms as the TBIs are obviously limited in the amount of air they can pump.

One thing I should note: although the stock amp is decent, I am running my subs with a pair Acoustic Reality ICE based 600 wpc monoblocks and I'm using a high quality external crossover set at 55 Hz with 18 dB slope.
Velodyne DD12 is also good. It is not perfect and there are tradeoffs. I have mine 3 1/2 ft away from backwall but I find 5 ft better ( when family situation allows.) Would say 3 ft is minimal. Try sound treatment, too.