I just got a Cubietruck and flashed it with the 1.5 Image.
Nas and Library are working fine, the build in DAC is working.
But I cant´t find any USB DACs in the Web UI under Audio Output. Both DACs I tried are working fine with CuBox + Volumio and are showing up in the audio output menu.
Under aplay -l the DACs are listed as card 4 and 5. I tried both USB ports and tried also with and without HUB.