Somehow the HD-580 is really, really good with the HRT Music Streamer II to my Fiio E9. The soundstage is quite large and bigger than through portable amps.
Not sure why the E9 is so good with the HD-580.
I switched to the hD-600 and the 580 is much more fun to listen to and the mids are more forward (but still accurate).
Currently using the 580 with HD-650 cable until I get my Double Helix cable back in the mail.
What's funny is that the 580 was the first expensive headphone I ever bought. Had it in 2002-2003 I think and I was so clueless and was driving it from a portable CD player I think!
So stupid...back then I didn't use Head-fi.
The HD-580 has a few similarities to my well amped Koss Pro DJ 100. Sounds a bit weird to say this. I've found the 580 to be better than the hD-600 despite the same drivers.
Seems to go against what everyone thinks.
BTW I haven't gotten either to sound good (maybe decent) from most portable amps. The only exception is the Total Airhead. The E11 doesn't do a very good job despite it being loud enough.