The paragraph immediately below further discusses the rear volume setting. While this may provide a dramatic effect for movies and music, eventually you will want to adjust your system so that the surround effect is much more subtle. In fact, one of the interesting things about a surround sound system as that you normally don't hear the rear speakers as a distinct sound source at all. I've also noticed that different material often requires a different surround volume setting. This is especially true for surround sound encoded movies.
Some movies require a larger rear speaker volume setting as their surround effects are very subtle.
Other movies have an incredible amount of music and sound in the rear channels and require a reduced setting for the rear speaker volume. If you have trouble hearing the movie dialogue it may be due to your rear speaker volume being set too high. In two channel stereo listening, audiophiles often try to achieve that delicate balance between too little or too much room echo. Too much echo and the imaging suffers. A recording of a symphony in a large hall will sound like it's being played in a large hall.