I'm looking for a (fairly) portable solution as a source for sensitive high-end IEM's. I know that these 3 devices are all slightly different in terms of portability (usb powered, battery powered, ac powered), but for now, I'm primarily interested in advice about sound quality. All 3 devices include a dac and an amp, and all three can receive audio via a USB... and these are the most important functional characteristics for me. Also, all three seem to have very low output impedances, which is important for my intended IEM usage.
So, I'll take whatever advice you guys can provide about sound quality. My two biggest criteria are detail/clarity/resolution and a low noise floor with IEM's.
If anyone can chime in, it would be much appreciated.