Cam, this isn't highly critical, especially with the QSs, but in a 7.1 setup where there're actual back speakers to provide the back surround effect, the side surround speakers are best positioned directly to the side(the 90 degree angle in the diagram). In a 5.1 setup, putting the side surrounds a couple feet farther back(similar to the 110 degree angle)lends a little "phantom" back surround effect in the absence of actual back speakers.

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Enjoy the music, not the equipment.