I suspect you are getting ALOT of room reinforcement for Audyssey to set QS8's at 50. I would set them at the lowest to 60 and as has been mentioned 80 is the norm. I would also raise the M60 to 60hz and switch back and forth between 60/80hz and then leave it where it sounds the best.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70