[MatrixDweller]

I was looking at the manual found on the Onkyo site. You basically want to turn off Dynamic Range Control and Dialog Enhancement in the DVD player, AVR and TV if they have those options.

Dynamic Range Control compresses the audio so that the bass is less and there isn't as much shift in dynamic range from one part of the movie to the next. It's good if you're listening at low volume, say late at night. Your TV could be doing this automatically or through a setting too. AVRs often have that feature too and call it either night mode or Dolby Digital Compression.

Dialog enhancement boosts the center channel. That should be done in the AVR by adjusting the speaker levels.

Have you tried using optical from the DVD player straight to the AVR (use the cable from TV to AVR)?