You can isolate your DAC from your computer quite easily. The majority of the the noise generated by the computer is in the power line that runs side by side with the data lines inside the cable.
A simple $5 USB adapter that removes the power from the cable and a powered USB hub does the trick for me. With the proper playback software my USB PC sounds better than the PI2AES using AES / EBU, I2s or coax.