Hm, wouldn't the source technically be the Hugo itself? But I have it connected via USB to my Sony Vaio laptop (and I'm ashamed to say that I almost prefer the sound of the laptop directly powering my 'phones as compared to Hugo.
The Hugo sounds more detailed and spacier, but quite a bit hinner, brighter, less bassy to me -- at least that is the case with my Ultrasone Pro 900s, the Fostex jack doesn't fit into the Vaio's headphone out, so I haven't tried). Same with my Sony ZX-1, can't plug the Fostex in there, but from memory I think that I had the same impression with the Ultrasone. The highs on the Hugo just seem to somehow increase way more than the bass with high volumes.
I seem to remember, incidentally, that there were others that described that phenomenon (audionewbie and hykhleif come to mind), so I'm not sure it's not the Hugo. Perhaps it's just the fact that the synergy is not my thing. That damn treble is just sooo hot! And I don't mean that in a good way. It would be interesting if others could chime that have had a similar experience.
Edit: I'm just listening to some vinyl rips I made myself, and things actually improve a bit; the sound is warmer, fuller, a little darker, all in all a bit more to my liking. The lower end improves, but still I can't dispose of that overly upfront treble.