On height, I think you'll find they're incredibly flexible. Keep them above ear height when seated for sure. In my theater, I've found that they sounded good anywhere from around 5' from the floor up to around 7', where I have them now. The key is to leave adequate spacing from the ceiling above them (at least 6-12" IMO). The reason I went higher is to keep people from bumping into them when walking through the room and to keep kids (or other unruly guests) from grabbing/poking/prodding them in the future.

Epic 80-800: HG Cherry