I think the iFi Nano iDSD is the best I’ve ever heard. The DAC/amp combination is incredibly clean. It has MQA, I don’t use that though, but if you wanted to it’s there.
The Rode AI-1 is a great desktop-only option too, also a fantastic DAC/headphone amp. It just bothered me because it allows digital volume control so you’d have to make it an aggregate device in OS X audio settings to disable that.
