I think that the crossover set-up you choose will be at least as important as the sub you choose. I use Rythmiks with small Maggies and they pair superbly IMO. However, I use Audyssey bass management and there's no doubt in my mind that it's a big part of this successful pairing.
As to the sub itself, Hsu, SVS, and JL all make some highly regarded subs. Some of the bigger Velodynes are also excellent. Many folks swear by REL, too.
As to the sub itself, Hsu, SVS, and JL all make some highly regarded subs. Some of the bigger Velodynes are also excellent. Many folks swear by REL, too.