Thanks Nickbuol, you are right I am over thinking this! Even though I don't have atmos and probably wont for a while since this is open plan living room I will do the stands and have it 90 degrees rather than rear wall mount it for better sound. I just ordered the FMB few days ago but I can always keep it and works on other speakers as well. My room is 18 feet long and 14 feet wide from side wall to kitchen short wall. Rear wall behind couch is 10 feet wide and 9 feet ceilings. I'm currently sitting 14 feet from the front speakers and my ears are 24 inches from rear wall. Do I have room for 7.1 to add rears? I can move the couch 1 more foot to be 3 feet from rear wall. I'm gonna add some pics. You will see I can have the stands on both ends of couch even though one side will be in middle of hallway or up against short wall during movies and then slide the stand to rear wall when not in use.
http://s1070.photobucket.com/user/ereed28214/library/Home%20Theater
