One of these shoudl be arriving today:
www.toppingaudio.com
I'm currently using a SMSL PO100 Pro as a DDC which I was generally happy with but seems to have some issues with some very specific albums/styles of music. The same things play fine when bitstreamed via USB to my Topping D70 Pro Sabre. I decided to try another DDC and see if I get a better result with those problem tracks. The topping does have a different USB conversion chipset version so we'll see.
The SU90 is tempting but I'm not willing to spend that much on an experiment. There are also some used Matrix Audio X's out there that are tempting too, but again a bit more than I want to spend on a "to try" right now.