Responses from cata1yst

USB Ext Sound Card Vs. Squeebox
Sqeezebox has a really good digital out, supposedly you will be hard pressed to find a difference between a good cd player as a transport versus the squeezebox + FLAC encoding 
Zune output vs. CD output
no you cant use a DAC with the zune as simply storage (i wish you could though)The stock headphone out is really good for a portable, but i highly doubt that it will compare in any way to a Cd Player.Why dont you get a sqeezebox instead? it can do...