I have a room that is 4,000 cubic feet and I can tell you that I don't think you need 7.1; 5.1 should do just fine. I even did testing (and there is a long post on this site somewhere) to prove it.

Look at Mojo's Dojo on Axiom's wall of fame. I did 7.1 and placed a ping pong table under a QS8. If you decide to do the same, you can justify a pong table that way.

Or, you can save your QS8 money and put it against an A1400 \:\) .

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated