You've been able to drive the HD800's with this? I know Focals, Grados and the TH900 are low impedance, but to drive those sennheisers is a different story.
Welp, I'm at a loss. Maybe I'll get one in the future and see what it can do. If you can, test other high impedance/low efficiency cans when you get the opportunity. Would be extremely helpful. Cheers!