Zute, first some comments on apparent misconceptions that you mention. If your Pioneer has a rated 110 watts/channel, you'll get at least that much "real" power since it would be against the law(FTC regulations)to use that rating otherwise.
As already mentioned, never use the lower impedance setting, since all it does it to reduce the voltage output and as a result, the maximum power capability.
You can't "bi-amp" with a receiver, despite any advertising claim to the contrary. The receiver has just one amplifier with one main power supply section, and this capacity can't be increased in any amount by adding extra wire connections.
Your Pioneer should have no problem in driving an M80/VP180 front line at all levels which won't endanger your hearing. The side surrounds should remain your QS8s. For back surrounds in a 7.0 setup another pair of QS8s would certainly be appropriate, but if you have enough room behind your listening position(say at least 6')for their sound to spread out, M2s would also be suitable back there.
