Sounds Like Sugar is all over this question, and I'm sure knows more about subs than I do, however just to through out another suggestion, the Paradigm Servo 15 is a very high regarded sub. Velodyne is also a great sub maker, but I think that it is geared a little more towards HT (it's not fast enough for music) but I wouldn't quote me on that.
Subwoofer for Both Music and HT
I have seen forums for subs for one or the other but not for both. Any opinions out there on subs that will work well for both 2 channel and home theater? I have Merlin VSM-M's in the front with a VSM-CC and an older pair of VSM-SE's for the rear. Appreciate any feedback on what has worked well in your systems