I always stay away from converters. Add extra stuff to the signal path is always a bad thing. I use what is native.
You're closer to the end state of your hi fi journey than many of us who are either starting or are in the middle of their journey. How about a little empathy? ;-)
I'm not going to argue the technical merits of USB vs. I2S but rather try to imagine that someone has a DAC with both interfaces and for whatever reason I2S sounds better?
I agree that putting DDC "barrel connector" in the signal path isn't optimal but if it provides a better listening experience by definition it can't be a "bad thing".
One day this probably won't even be a consideration as the technology will have sufficiently advanced such that we can get the integrated Streamer/DAC that is emotionally engaging and at a reasonable price point. In the mean time, we all do what we can, the best that we can.
ps. Love your system! Although I can't see it anymore. I haven't been able to see Virtual Systems since around the time they instituted "bot checking". I suspect I am not alone.