Ok, I think I have narrowed down a list of subs to think about:

HSU STF-3 ($599)
HSU VTF-2 MK 2 ($499)
Klipsch Sub-12 ($450)
SVS PB-12/ISD ($599)

I really prefer 12 in sub but if furniture and stuff kills all the money, I would probably consider the PB-10 for $429.