Yes Drew, as some of the other replies have also indicated, receivers(your 2600 will have DPLIIx)have processing which extracts some of the sound(which belongs in surround farther back)which is naturally present in the two stereo channels or the side surround channels of 5.1 source material and steers it to surround speakers to give a better effect. In fact, the 6th channel material in a DD EX disc, which would provide a mono back effect, isn't used when DPLIIx is in effect. Instead material is extracted from the left side surround which should go to the left back and likewise for the right side, providing a stereo rear effect.
