Best DAC to pair with Anthem CD-1?

I have enjoyed my Anthem CD-1 for 10+ years. It was designed in 1998 and I can't help but think that current technology can provide noticably improved sound. I have decided that the best way for me to go is to add an outboard DAC that will offer the flexibility to eventualy move to (not exclusively!) a computer based music server. With that in mind, I would appreciate recommendations on a good DAC to meet my current and future needs. Below is the rest of the requisite system and budget information:

Amp - McCormack DNA 500
Pre - C-J ET3-SE
Speakers - Aerial 10T
$$$ - Around 4k and I don't mind used.

All recommendations, suggestions and opinions are welcome and appreciated!
FWIW, i have enjoyed the newer Wadia DACs a lot. to my ears, i have found the newer 2 generations impart quite a natural tone in the right system. I have heard ARC, Krell, Zanden, Esoteric, Stahl-Tek, and a few others.

My favorite is the Zanden which, second hand, might just be a margin above your budget (or perhaps not). The key is the Zanden is 16/44.1 only, so you might wish, given your stated desire for future needs, to have greater flexibility for hi-res. good luck.