Adam, on the QS8 question, one thing to keep in mind is that in a 5.1 setup they're side(not back)surrounds and should be separated widely enough to give a side effect even if located a bit behind you. A location on the back wall about 6' up should be fine, with the left one just a few inches from the side wall and the right one separated a bit farther than shown in your diagram, so that it's definitely to the right of the couch.

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Enjoy the music, not the equipment.