Unable to answer your question about the differences in DACs, but look forward to someone else answering it.
It's a refurb, although they use the term "Reconditioned by Denon." PCMall is an authorized refurb dealer for Denon. I think your chances of getting a refurb lemon, are about the same as, or perhaps even less than, getting a brand new lemon. But, that's just my opinion. The biggest disadvantage in going the refurb route is that you only get a 90 day warranty. If I were in the market for a new receiver, and I may be in the near future, I'd take the chance. But again, that's just my point of view. YMMV.
