Bryan, the QS8 should have at least a little breathing room for the bottom woofer, which can be arranged by raising it an inch or so with wedges if it's on a solid stand.

More generally, if the QS8s provide plenty of dispersion as side surrounds, the more direct M2s could well be considered for the back surrounds. The M2, positioned vertically, also serves well as a center speaker.

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Enjoy the music, not the equipment.