Funk, welcome. Since the room is 16' long, the back of the couch is roughly 3' from the partition behind it. If that's actually a full wall rather than some type of counter it would be suitable to mount the QS8s on it about 6' up. The right side surround would be out wide enough(at least for a listener in the middle of the couch)if that section that extends at about a 45 degree angle can be used for mounting.

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Enjoy the music, not the equipment.