90 day update:
Now, that the D90 exists, it's difficult to praise the D70 as being the best of the best, anymore. The D90 also offers Bluetooth, and there's a MQA version coming. Also, the D70's AK4497 is a little slower, and so has a gentler bass presentation. Actually, it affects more than just the bass. The D90 should offer more slam, and impact in all frequencies. So, if you have the money, you'll probably want to be buying something with the newer AK4499 chip, like the Gustard A-22, with its alluring fully custom Class-A discrete logic and power circuits in lieu of ICs. The D70 is still a great option, though. So, if you're looking to save a little money, you won't be disappointed.
I chose the D70 over the more expensive ESS chipped DACs, because of it's flatter, more linear response curve. I figured it will pair better with the 789, and allow me to get a nice flat, uncolored, linear and transparent reference point. They are also about evenly priced, and so they are quite the pair. I feel like I got exactly what I was hoping for. It sounds almost perfect. However, I can feel that gentler impact, which does leave me wishing for more.
I also like the large display, and it has 3 brightness levels. Despite what a certain website claimed in their testing, it's plenty bright, even on the lowest setting.
The only missing features are MQA decoding, Wi-Fi streaming, and Bluetooth. However, you can easily add the Wi-Fi & Bluetooth capability with a cheap singleboard computer, such as a Raspberry Pi, and for a fraction of the price of the more expensive models. MQA decoding can be handled by software, and it's a digital technology (occurs prior to audio processing), so you won't notice any difference. Thus, it's not missing a single thing you really need.
The PCM filters come in very handy when tube-rolling, as it makes it possible to match/correct the characteristics of your tubes. I was actually hating a new pair of tubes I spent a lot of money on, until I figured out that all they needed was a little extra delay and roll off to soften them up a bit, and so they sounded much better.
Also, mine arrived with 220v selected, so I had to manually switch mine to work with US power standards. It's as easy as flipping a switch, but just thought I'd leave you this little reminder.
Would recommend to a friend.