Hi alamakazam,
We'll see what others post, but I will add that for the Bellina (with PRO dac), we use Async, integer-mode USB to I2S
conversion. I don't recommend using a USB to SPDIF converter, as then you'll have to go USB to SPDIF and then
the dac will have to convert SPDIF to I2S, and it probably won't sound as good and going USB direct to I2S.
All the best,
Vinnie