Let me just say first off that I do not have much experience reviewing audio gear, so take it easy on me and take the review with however much salt you'd like, anyways - here goes...
Just out of the box now and hooked up, and I really think it sounds incredible. So much power! More than one would really need i'd think. First up, I tried the headphone out, and it sounded incredible and generally I was extremely pleased. My only complaint is that for now (seeing as it has yet to burn in) the bottom end seemed a bit ah, whats the word, "busy and somewhat lacking definition" is how I would best describe it. From what I hear this will go away with burn in.
Second, I hooked the tube-out directly to my Hitachi HMA-6500, powering a beautiful pair of JBL 4311b's. The sound was out of this world for me. Quite different sound entirely, and such power! The D1 drove my speakers to more than loud enough levels at just 12 o'clock. When no music was playing it wasn't quite silent, but I wouldn't call that much of an issue, it wasn't bad. Although strangely, I seem to be getting a small amount of intermittent feedback when no music is playing, almost like a very quiet hiss every now and then - possibly a power issue?
As I sit here listening to Aja, I can't help but be transfixed by the clarity. Once again forgive me for my lack of audiophile reviewing experience, but a word i'd use to describe it would be agile.
Overall, I feel the unit is unbeatable for the price. A solid headphone amp, and a tube amp that was more than I expected. My only complaint at the moment (which I hope will clear up) is the bass which I described above. Besides that, this has been a tremendous improvement in sound, and i'm quite happy with it thus far. In the future, I think i'll replace the tube, and experiment with OPAMPs (soon as I figure out where I can get some without ordering 100...)
A week or so, once its burned in a bit, i'll post more perspective, I feel like I have a few comments to add about the exterior too...but thats all for now, hopefully this review didn't turn out too bad.