Daniel wrote an article regarding playback music from computer for this issue “Enjoy The Music.com”

http://www.enjoythemusic.com/magazine/manufacture/1208/

“With the rising popularity of computers as a music source, more and more audiophiles are asking themselves whether a computer can be a decent playback system, similar to e.g. a CD Transport. To answer this question we have to identify the potential sources of disturbances. In digital audio there are two main factors responsible for the quality of a playback system:

1.)  The  proper transmission of the bits, i.e. a 0 must stay a 0 and a 1 must stay a 1.

2.)  The proper timing during sampling of the analog signal (A/D Conversion) and during D/A conversion.”

It’s a simple good read.