I love my dacport. I usually carry another USB drive filled with foobar2k portable and flac/mp3s. It's a very transportable system. Used to have first Duet, it's too attached to MAC because of firewire. Plus, I think dacport sounds better.
Beware of headphone selection, if you are a bass head, you may find the dacport's bass anemic. But it handles all my headphones very well. Should've kept your HD580 though, they sound great out of dacport.
Good luck.