So, I switched to JDS Labs The Element. More than capable of powering any pair of headphones you throw at it. There is something addicting about the large volume knob on top of The Element. It's a good feel interface that is superbly made. I also love that the DAC remains active with the power switch off. So my externally powered speakers can make use of it when I'm not using the headphones, and I do not have to unplug them.
Here is a review of The Element by user ZeosPantera. This should cover what I have not.