Does anyone have a suggestion for a DAC under $500 or so?

I have Vandersteen 2Ce Signiture speakers with Rotel components. I prefer to use cheaper DVD players because of their wider compatability (Divx AVI, WMV, mp3, etc), but the quality of the analog output is lacking in these cheaper players. I would like a DAC so I can use whatever cheap DVD player I feel like using that week, and not compromise audio quality.

Unfortunately, the M-Audio Flying Cow DAC does not have optical input, so it is not an option.