you can do that with any computer to a USB DAC such as Benchmark, PS Audio or Bel Canto. A very easy way to do it is with a MacMini.
Direct USB computer to coaxial outboard DAC
I am looking for a way to bypass a sonos or apple TV. I want to know if there is a cable that goes from computer usb to either a coaxial or toslink connection in outboard DAC? If not possible what would be a cheap alternative without sacrificing sound quality?