What would happen if you swapped just one of the + or - sides for the fronts on the back of the receiver? Say swap the left/right - wire, and left the + side normal...
_________________________
M80s-VP180-QS8s-EP600-2xEP350 Denon3808 Outlaw7700
M22-OWM22-VP100-Denon2805
Audio Nirvana