The S/PDIF route is interesting, it might be the closest option, I think the card you linked to actually only does spdif output. I'll investigate this further.

The S/PDIF route is interesting, it might be the closest option, I think the card you linked to actually only does spdif output. I'll investigate this further. I'm probably going to order some USB > i2s chips and optocouplers and build something myself.