About the movie audio thingy

"Dolby Digital/DTS/etc are generally mixed for a wider dynamic range while stereo is generally compressed for a narrower dynamic range -- i.e. basically what ViRGE said." So basically there's more range, quiet stuff is more quiet and louder stuff is more loud, but we probably don't notice those parts.

Thanks to Virge, Madcow, and everyone else who answered in the thread. If you're interested in the subject, check out what they have to say about it.