Sub to match PMC TB2+

I'm looking for a sub to mate with my TB2+ speakers. I have the TB2's bi-amped and bi-wired to a pair of ATI 602 amps. In front of the ATI's I have a Musical Fidelity X-10v3 Tube buffer. I use a NAD 320BEE integrated as a pre-amp. CD is Musical Fidelity X-RAY.

Room is approx 12 by 17 with a lot of listening done in an adjoining room which makes the distance from speakers to ear about 20 -25 feet. I love the sound of this setup although I'm sure it could be better. The main thing I think may be lacking is the low end. The TB2's do a phenomonal job on the low end considering their size but I can't help but feel that I could get more out of my music bass if I added a good sub. The PMC sub's a way too expensive for me. I'm considering picking up a Sunfire True EQ. Does anyone have any comments on the potential for this type of setup?

I listen primarily to rock/blues/jazz