What, you mean have the Foxsat-HDR output audio via the USB port in realtime? If so, no.
If you mean taking a video file the Foxsat-HDR has recorded, copying the file to a USB device, connecting that device to a computer, extracting the audio and converting it to some format other than MP2/AC3, then yes.
Agreed; I have my Foxsat-HDR hooked up to the amp that way as the two opticals were in use (Xbox 360 and HTPC). The co-ax functions the same way with the optical converter. Only caveat I have with the Foxsat-HDR's optical is that it outputs more quietly than the other devices - I think this is true about all the audio outputs actually. This means a poorer signal-to-noise ratio on the analogue ones (SCART and dual RCAs) but less chance of distortion on any.
Anyway the optical to coax converter I used was this one from Amazon. Ordered via Cable Mountain: dispatched within 3 hours, arrived within 48 hours. THAT'S service.