I recently went on a mission to find a good sub in the $500 budget range, and
after about 8 listen/test outings, bought the Definitive Technology ProSub. I
only use my sub during dvd playback as my main speakers have no subwoofer
issues( I played around with it for midrange help on some tracks) but for surround
sound movie soundtracks, it's a very good speaker at the $500-$550 price
point. Also it carries a 3yr warranty on anything in the speaker, even the Cab
which is unusual. If your sub hunting, give this one a listen.