Unfortunately, due to the room layout and configuration I may need to mount the L & R surround and rear surround speakers (7.1 system) from the ceiling. Would this cause problems with the 'imaging' of the sound? I.E would it not sound right as the effect sounds would appear to be coming from above you?
I have installed a couple of HT systems with ceiling mounted speakers with decent results. Keep in mind the speakers should be just behind the sweetspot for viewing. With aimable speakers these days you can come pretty close to assimilating wall speakers. There are quite a few on the market and vary greatly on price. Keep in mind your doing something that a wall or satellite should do so it may cost a few extra bucks.