If I'm going with a twenty foot spread between the QS4's, I wonder if alot would be gained from putting the QS4's on the side walls. Of course, that would involve convincing my wife to let me put a speaker on the fireplace wall - don't think that will happen...

I'd always origionally envisioned a back-wall mount positon only being about 10 feet apart becasue I thought you were supposed to try to match the spread of your fronts...