Swirv, in a 5.1 setup without back surround speakers it's desirable to have the side surrounds slightly(say 2')behind the listening position to give a little "back" effect, both from being a little to the rear and from "phantom" imaging sounds equally loud in both speakers as if there was a speaker in the back middle.
When back surrounds are added for a 7.1 setup, this positioning of the side surrounds toward the rear isn't necessary, since there're real back speakers. In that case the side surrounds can be positioned directly to the side, for possibly a bit better purely side effect, although with wide dispersion, such as the QSs provide, it shouldn't really be a critical adjustment.
