Chris, welcome. Yes, the QS8s are outstanding performers as surrounds. Since you'll be using the Sonys as back surrounds, the QS8 side surrounds should be mounted directly to the side of the listening position if possible, and about 3' above ear level. The back surrounds should be separated by about as far as the distance that they're behind the listening position, assuming that's enough to put them outside the listening position both on the left and right.

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Enjoy the music, not the equipment.