Best sounding CD Player for $3K or less used?

I assume you are talking about a redbook player, and not a universal player. If so, you might consider an Ayre CX-7e at around $2K. I also have been looking at different players in the $3K or so range that might significantly improve my system, but I have yet to hear of one that makes me want to upgrade for primarily redbook playback. Maybe the Ayre has good synergy with the rest of my system, but I think it might just be a pretty good player. BTW, I use it single ended, but I have used it both ways and in my system it sounds just as good single ended as it did balanced (with different preamps).

A used ARC CD3 MKII would be worth considering.

In no particular order...

REGA Saturn

Meridian G07

Meridian G08

Meridian 508.24

Esoteric DV-50 or (DV-50S)

Wadia 301

Wadia 302 (heard it is very similar to the 301)

Wadia 830