Hi Reason 1,
In terms of producing a nice sense of envelopment, Quadpolar surrounds are usually less critical for placement than direct-radiating surrounds. If you must put them on the back walls, get them up higher (several feet higher than your head from a sitting position). It's my experience that quads are more accommodating to side or rear-wall placement, and less fussy overall to align than direct-radiating surrounds. Actually, mine are at different heights in an asymmetrical setup and they work very well.
Regards,
