every room is different Bryan, you will need to experiment. I found that if I have my M80's pointing about 2ft behind my head it sounds great. My M80's are about 11-12ft apart and I tried many variations before settling on this.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85