If you are committed to the Apple platform, go here:
http://www.empiricalaudio.com/computer-audio/, as well as the Computeraudiophile web site I recommended earlier.
In short, use Amarra in lieu of iTunes, rip to lossless AIFF codec and use a high quality USB cable or SPDIF on RCA if you Mac accomodates it. The iPad info above is spot on. The DAC Magic is a very high value DAC at the price point. It only does 16/48 on USB, though, if that matters to you.
Full disclosure: I have a DAC Magic for sale on Audiogon with the outboard Pangea PS. I am selling only due to stepping up in the DAC world - see my related post in the digital forum. No issues or complaints with the DAC Magic for what it is.