I had my surrounds mounted forward of the main listening positon and adding a rear center channel greatly helped my surround field, but I was corner loaded(TV in a corner with seating on the opposing walls to that corner which left a BIG void in the Middle. I am going to try a single QS8 above the main seating once I get into my new house, so I will let you know \:\)

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