Maybe a dumb question but just to make sure there are no assumptions - when you say CD in the PS3 you are referring to actual 'factory produced' audio CD's? i.e. not MP3's burned on a CD that could have some digital gain tags applied to them that could be causing this effect?

Also as you suggested, go through the PS3 menus and make sure all volume normalisation options are turned off.

Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1