I'm currently running M22ti mains, VP150 center, the Hsu VTF-2 sub, and some Polk Audio surrounds through a Rotel RB-1075 amp (120x5) and the Rotel RSP-1066 processor.

The reason I ask the question is that perhaps in the future if I feel the need to jump from 5.1 to 7.1, I'll either buy a pair of M60's for the front and move my M22's to rear duty, or keep my M22's as mains, and buy a pair of QS8's for surrounds and move the Polks to the rear.

In either case, the main's would then be being powered by a separate amp. Probably the Rotel RB-1070 (130x2)

It would certainly be less expensive to purchase a pair of QS8's than it would M60's, but would I be missing out on much?

If floorstanders are the way to go, M60 vs M80? I've seen some really good prices on some M80's on Ebay recently. Is it worth going all out and getting the M80's over the M60's? (Recent Ebay prices being between $650-850 for the M80's)