outputing digital audio over USB port to external dac?

I am on the fence about getting a MacMini or an AppleTV.

I want to create a music server and output the music in digital
format to an external USB DAC. I know AppleTV has TosLink but
I want to use a USB DAC.

I read that aTV enables the USB port. Does aTV (or any other hack for that matter)
allow you to send music digitally over the USB port to an external USB DAC?