Regardless of where you put the speakers for a "5.1" setup, your 4th and 5th speaker should be hooked up to the "side" or "surround" jacks on your receiver and not the "rear" or "back" jacks. When you add your 6th and 7th speakers, they will be setup as the back speakers.
I know many here have their 5.1 with the surrounds behind them for the simple fact they had no place to mount them. For someone like myself with no side walls anywhere in my room, I bought the Axiom speaker stands so I could put them on both sides of the couch.
Either way, I'd go with the QS8's.
