[Jeezer]

Yeah, back when I had a different audio interface with a less decent headphone amp built in, I'm sure the on-board D-Command headphone socket was sounding more detailed and revealing vs the interface HP out.

The ICON Headphone socket feed, comes back up the control cable (that goes between D and Xmon), so it's sent internally from Xmon, tapping into I guess the same decent quality that your interface analog outs are sending into Xmon analog ins. It seems to just forward that to D-Command, not sure if the headphone amp is in the D or in the Xmon itself though, but will assume in the D not that it matters. So that xmon/D headphone amp that derives its signal from your (on some interfaces) better quality line outs vs the interface's built in HP socket appeared, from memory, to send a very clear signal back. And the HP amp itself appeared to be pretty decent.

I can't say it if sounds better than a separate high quality HP out on something like a Benchmark, Hilo or whatever but seems it's a non issue as far as passing decent audio through the unit.