Project86 just said the Izmo M1 sounds spectacular feeding SPDIF to the D2. M1 is using a low jitter TCXO as clock. I don't know the p/n of the clock M1 is using, it may or may not be better than the Crystek I used in your D2 mod. In any case, TCXOs should have much lower jitter than the clocks Anedio is using in D2. So one more data point to show that D2 has room for improvement if it is fed with a lower jitter async USB converter.
To be fair to Anedio, I never got to compare the Izmo M1 to the integrated U2 directly. And I can't until I get the USB input working again. Also I was feeding the D2 from a laptop or a modified SB Touch, but now I have the Auraliti PK90. So it's kind of apples to oranges for now.