I think eventually I'd like to put the M3's in the rear, QS4's on the side and some M60's up front.
As far as a subwoofer, I saw a DIY system at partsexpress.com that has a 10" driver, 250W amplifier and claims to go down to 24Hz in small to medium sized rooms. For $350, I'd give it a shot. But for now, my A.R. sub will do just fine.

Big L