From your question and the responses above, the dilemma seems to be: With a computer there would be inconvenience, but you could get decent DAC without any jitter problems (i.e., the HRT Music Streamer II) for very low price (Better yet, going for the II+). On the other hand, if you go with Airport Express or apple TV, you will need a considerably more expensive DAC to make it worthwile. The Airport Express is subjective to jitter, and Kijanki's point is a very important one. If you go that route, I would recommend a DAC known for great jitter supression such as the Benchmark. Alternatively, you could go for a reclocking device such as one of the Monarchy Audio DIPs, which can occasionally be found here used for about $100-200, along with a less expensive decent DAC such as the Musical Fidelity V-DAC.
Good Luck!
Good Luck!