Hi KungFu,
When movies and shows are mixed in Dolby Digital 5.1, the dialog is often mixed too low because the director and sound engineers have heard it dozens of times and know it backwards, so they tend to bury it in the mix. The whole point of an adjustable center-channel level is so you can increase it for your room and system so it's completely intelligible.
I routinely run my dialog channel at +4 dB or +5 dB above the front left and right. You may also be running your surrounds much too loud, which new listeners to surround often do. They are for ambience and you shouldn't "hear" them in the conventional sense. They should just open up the spatial character of any scene and provide ambient cues when the latter are hard-mixed to a surround (sounds like a door opening off-camera or similar cues).
Regards,
Alan
