The sub market is flourishing with great inexpensive subs, Axiom, SVS, Hsu, epik, elemental Designs just to name a few. Pick which ever one you feel is the right size and price from any of the usuall suspects listed on the AV boards and you won't go wrong.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70