Allan, if the rear surrounds will be about 3 feet behind the couch, the side surrounds should be a foot or two in front of the couch, but this isn't really a critical measurement.

So far as the gauge of the speaker wire, there's nothing special about the 10' distance you mention, although at that distance even 18ga would be more than enough. If you're actually thinking of a run of possibly 30 feet to rear surround QS4s, then 16ga would be fine. The wiretablein this article shows what you need.

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Enjoy the music, not the equipment.