Great review. I think part of your enthusiasm is that you have never heard an amp at these distortion levels. A lot of us Neurochrome builders and Benchmark/NCore/Orchard Audio/etc... owners have and are kind of used to it (in the loudspeaker world). We expect it. The Neurochrome HP-1 (discontinued) was somewhat the progenitor of this in headphone design and my colleague in the RTP area has one which he listens to everyday. What will be interesting is a shoot out between Tom's new budget kit, the Neurochrome HP-2 (which will be arriving to me in a few weeks), the original fully differential Neurochrome HP-1, and of course the Mass Drop/Monolith THX headphone amps. That should be an interesting comparison which we can probably arrange, since we live close to one another. I don't think there will be dramatic subjective differences at these distortion levels to be honest. But if we were to switch back and compare to any of your Bottlehead builds or Hagerman's recent unit, or Noir/T2, I think the differences will come back to being STARK! Whether that is subjectively better or worse is up to the listener.
Mind you, your achilles heel, or what is holding you back now, is your source or DAC. You cannot get any more detail, "downward" dynamic range, etc... than what your dac can deliver. So I'll haul over my dac too for the comparison which should be fun times.
Happy Holidays! And enjoy your new present!