I'm currently using the built-in CD player on my Pioneer DVD player, with an optical digital cable out into my Denon A/V receiver. Most recently, I tried this against an older dedicated Marantz CD player, and could not tell any difference. Of course, I have tried other players in the past, and I could not tell much difference between them. I've never used a very expensive unit.
I'm not saying that there is no technical difference between a $50 CD player and a $3000 one, but maybe no audible difference. This, as other members on this forum have pointed out, has been shown in double-blind tests. The technical differences in the design of CD players, and the fact that you cannot design perfect filters, plus other technical differences, does to some extent justify the higher expense of more pricey units, in that you are paying for better design.
What is the point though, when the higher quality does not produce objective audible improvement? I do understand that one possible failing of this augument is that DAC's will produce noise depending, in a quite complicated fashion, on the program material. A good CD player unit will suppress this noise into the subsonic region. It's not enough to use sine wave patterns to check for this. The test must be designed to take these sorts of things into account.