J.R.,

I agreed with a lot of the previous comments here. You need to tune your system. In a lot of instances the rear surround speakers have a lower sensitivity than the front (which means they aren't as loud), so you need to introduce a Test Tone to balance them.

As Bevan mentioned earlier, a number of movies are 5.1, but sometime the surrounds are not that active, so don't be surprise if you don't hear anything...