First how the heck are you getting prices like that legally?
Second, I just bought a SC8000 (at a far,far greater cost).
And while I've never had a good sub before and never heard and of the ID subs mentioned here I don't think you'll find one new with shipping that would out perform the SC8000 or Reference at those prices especially if you were to get a pair of either.
Klipsch RF-62II, RC-500, RS-400, SVS PC12+,
Def Tech SC8000
Harman Kardon AVR 1600
PS3, Apple TV, Sharp 70" Qattron