If the sofa was only 1-2 feet approx from the back wall is with worth considering a 6.1 or 7.1 set-up? Could you mount the speakers high and point them down? Also when using a 6.1 set-up could you use a centre (front) speaker for the centre rear channel or would it be best to use the same speaker that's used for the surround (side) channels? Thanks in advance. Rob.