I own a D2000. The one fundamental complaint I had about the D2000 was that it was fatiguing and very bright. And I listen to whole albums so long listening sessions (70 minutes at least) are the norm for me. On a lesser note, that the bass was on occasion overpowering.
I have been considering upgrading to the HE-400s plus a Fiio E17. This thread has convinced me I'm making the right decision.