Without a doubt, USB units like the Regen work. I use it and the USB unit from iFi with the Auralic and the Aurender to improve the sound. Which does not mean that they did not implement the USB output to be the best it could be... obviously it could be better, but this is the best they "could" implement (cost). Even the DAC guys feel that what they did at their end is the best that could be... but many agree that outboard products do improve the sound on their DACs.
Have heard some interesting things about the Sonore microRendu... tell more?
I know the Uptone Regen kicks my Aries' performance up a notch.
Plus, the Sonore microRendu now on hand may take USB performance to a whole new level than previously available.