Speaker upgrade

You may want to listen to some vandersteen 5a or quatros depending on your buget very much the same sound as Thiels. I had the same bass issues now I have the 5a couldn't be happer. The trick is they have there own powered subs that are phase correct in the speakers. This produces tons of fast bass and also provides a natural by amping so if you run high end amps they just need to consentrate on the mids and highs. I have found subs never really work out well they just don't match the speakers 100% or the volume is not consistant. The Vandersteens also have a very advanced crossover that gets tuned to the room and your equipnment so you can alwas tweek the bass for more or less bass.

How do you spell D-U-N-L-A-V-Y ?!?

You want vocals? Jazz? Check out quality electrostatic speakers from Soundlab and Quad.

i've gotta say it. a mac pre and mcd 205 will nail realistic bass in any average size room with the thiels you have. you won't give up midrange to get it either. the musical fidelity plays....the mac controls

Bass, Bass, Bass, Bass and Bass and more Bass.
Get three subs (three is better than two in the sub department) and if it's not enough rip the tweeter and put a woofer in it's place.

Ok, we want bass, but the bass that exist in the music, not coloration. We dont need speakers that play below the 30 Hz, instruments dont go there, unless you hear organ music. Even if your speakers go to 25 Hz 0 dB, thoes your room has space to give this frequencies.
I'm not an adept of a sub, if you want better bass change your speakers, dont buy a sub. Inplementing a sub in a audio room is difficult, and most of the time the results are only satisfatory.
The question is - What do you want? Better bass; or as someone put it "room filling impact without boom."

Warrenh, could you please explain the concept - Power plus room nulls avoided - when two subs are used.