I have a similar problem and I am playing with the location of the rears. Right now they are 1.5' behind, 2' up and 3' to the sides. I am trying them 1.5' behind, 0' up and 1.5' to the sides using Gladiator, U-571 and Master and Commander battle scenes and the Star Wars pod race as the test sounds. I want more separation out of the rears, and want the sound behind me as it is supposed to be, but because of furniture placement, cannot be so placed. Bottom line, get some test scenes and by trial and error, find the best placement for your seating arrangement and room acoustics. Bearing in mind that the "best" position would be directly behind, forcing you to relocate the seating position forward a couple of feet. A near second best is slightly off center and toed-in. Let us know what works best for your situation.