Thanks. I read that in the manual, but I was skeptical of the 'available independently'. They could be meaning physically independently, while still just a clone of the analogue. I don't entirely trust manufacturers. Weirder things have happened!
Cheers, you've told me what I need to know, so I can now move forward in getting just a little converter box (Amazon do little ones for about £30). I'm not too concerned about a little bit of latency, as it's just to squirt out a backing track and reference material to the cans.