I've had experience with five under $500 players in the last month or so and been able to A/B them pretty thoroughly in various combinations, the Music Hall CD-25, a Cambridge Audio 300se with upgraded opamps, an AMC CD8b, a Philips 963 DVD/CD player and a Toshiba 3950 DVD/CD player. With that many options and a fairly small price range, it's impossible to say just one was clearly best but here are my observations.
If you've got $500 that you don't need for anything else and are interested only in the best two-channel audio, get the Music Hall. If you want to spend that same money and are willing to give up just a little audio quality for high quality video and the potential for multi-channel audio, get the Philips.
If you want to spend $100 on sound and $400 on something else, and you can live with a little less quality, buy the Toshiba (or a JVC 600 series DVD player.) The two players in between, the Cambridge and AMC, are also very nice for the money, both between $100 and $200 used, sound somewhat better than the inexpensive DVD players and the ergonomics are better.
They all do a good job for what they cost but the Music Hall is the only one that makes me stop when I'm walking through the room and just sit down and listen.