Steve:
I would strongly suggest a Totem Kin powered sub. They have them on sale right now at the Totem website for $500 ( regular price is $800). Sound and build quality are off the charts. Probably the smallest sub I have ever seen too. Sealed enclosure, 8" rigid carbon fiber woofer, magnetic grills. One of the most un-colored subs I have owned. Does not muddy up the lower midrange like most subs priced below $1000, even when the crossover is set above 100hz. This sub actually improves the lower midrange when used with small to mid size main speakers. A true audiophile subwoofer for those who appreciate music and not "boom"!