Well, I bought one on Amazon, and it worked out of the box. There was some weirdness with the power supply- it came with a European plug and a US adapter... SMH. I ordered a mean well 15vdc 1.2A wall wart. I've been listening to it for six hours now, going back and forth between this and my Schiit stack(USB Bifrost w/ original 4399 boards, Asgard 2) with my trusty Fidelio X2. I don't know if it's a house sound thing or what, but I like the Schiit stack better despite it not being quite as clear. If I had to put numbers on it, it's like the DX3 Pro has a 5% bump in clarity over my Schiit. The stack just has better authority in the bass region- a little more nuance with a little less effort, like it's not working as hard as the Topping. No argument that it's got some haze or grunge blanketing the sound, but what's there is more engaging.
I think my tastes run toward "flavored" instead of dead neutral. I love listening to midrange-forward, slightly rolled off highs, and big bass. That puts me squarely in hybrid tube amp range, or in this case, pure inefficient class A. I'm glad I have the Topping, and I'm still looking forward to the D70, but the DX3 Pro is going to get moved around a bit. It's too neutral for just enjoying the music in my reference setup.
I realize that at $219 (plus $20 for a shipped US wall wart), it wasn't designed to be "reference" quality, but it's very good for the price and offers a lot of utility. I'll be happy to use it with the xbox, and my computer, and my girlfriend's computer, and wherever else I plug it in. It just won't replace the Schiit stack as my primary headphone rig.