I thought this one would come up sooner or later.
The HD800 - moddable without audio engineering skills, efficient enough to sound good through most desktop amps. Good enough to be truly great through some amps. I have listened to the SR009 BHSE setup a few times now and that truly is great.
I have heard the HD800s through a First Watt F6 diy build I happen to own and am happy this and the HE-6 is as good as I need.