I'll just comment on one aspect from my experience vs. make a choice for you.
In the TV room in my basement, prior to my HT room, I was forced to mount the QS8 sides high at almost ceiling level due to the room configuration. The design of the QS8s diffuses the direct speaker location effect more than many speakers but there were some times that the height of the sound effects was a bit distracting. Seemed to be on the sharper effects. A door knock that seemed unusually high, that sort of thing. 98% or more of the time, it was fine.
Surround effects in 5.1 are technically, side effects so behind is not perfect either but again, the large majority of the time, you may never notice that.
In short, I wouldn't worry about making it perfect, as often a room prevents perfect and so the best you can go for is a solid 98% and enjoy. The main thing being... enjoy!
