I am looking to get a set of speakers with wall mounting dipoles for the rears. The problem is, the walls adjacent to the seating position cannot take speakers near ear level (since these areas are taken up by doors). The only place to mount them would be at a height above the doors. My question is, does the height matter for the positioningof reas speakers? Also, should the speakers be directly to the side of the listening position, or can they be slightly behind aswell?