I see eye-to-eye with Jeffreybowman2K's comments, but would add that if you buy a used iBook (good idea as they are plentiful and inexpensive), I'm not sure if they are compatible with the AppleRemote (you listed a remote as a requisite). In that case if you use a music server, like Olive or Squeezebox, you can use one of their remotes. I'd guess your budget won't include that though. I'd also second a vote for Wavelength's gear. I had their Brick USB DAC and it is a very nice DAC indeed.
Marco
Marco