Much difference between the two in way of performance for surround in general, and say the Qs8s vs M50?

The way my rear walls are, I would need stands for the Qs8s, the M50s would eliminate the need for stands which ups the price to use the Qs8.

My first post here so a little about my setup. My M80s and vp150 be here next week \:\) Currently using Klipsch RC 62 center, RF 62 fronts, and RF 52 rears using a B&K AVR307. my sub is a SVS PB12Plus 2.

My amp question. I am thinking of getting a 2 ch amp to drive the m80s, could I use my B&K as the processor and still use it for my center and surrounds? Thanks