Ya know guys, if you want to make a relatively minor investment for a big improvement in CD playback from DVD players, buy a decent (and that can be modestly priced) outboard digital/analogue converter. You can pick them up used sometimes for about 100 loonies if you look hard enough.
I have a Theta Cobalt and an HDCD Theta Chroma hooked up to my el-cheapo Panasonic DVD-Video player and Toshiba SD-9200 DVD-Audio player respectively and the improvement in both is amazing. I also have an EAD unit, but that is getting pricey. Audio Alchemy made some decent ones and you can usually find them around as well.
Never mind the 'built-in' DACs in most receivers ... they are usually pretty sad ... and use the coaxial connection rather than the optical, if you want the best sound quality.
Cheers, Mike.