John, that's another option I've considered. I really like the idea of the infinite baffle sub. I think I can build an array of eight, 15" drivers with amps for about $2500. That's more boom for the bang than just about any other configuration.
So with that, I'm already giving up 3 feet of the room's depth for the IB's manifold. That's perfect for installing in-cabinet speakers.
But yeah, I could get a couple big subs and place them in the room, and have real M80s behind the screen. That's definitely the way I'll go if the IB doesn't work out.
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs