Curious Cable Regen link update: This is an 8" USB cable that looks very well built made in Australia for $120. It is designed to replace the stock hard USB adaptor that comes with the Regen. There was an immediate improvement and I've been listening to it for several days now. Rob, the designer says that he cooked it on a cable cooker for 48 hrs, but that it still needed a few more hours before critical listening. My experience was that after the immediate improvement, it continued to improve.
In comparison, it makes the stock adapter sound 2 dimensional and lifeless, although that's not how I would have described it before. The most notable improvements I hear are a more realistic sound stage, with more space between instruments. It brings another level of naturalness to music. Everything is improved.
As an experiment I swapped places with the curious cable and my Black cat silver starlight USB cable which I use as the input cable into the Regen. It wasn't as enjoyable this way. It still sounded good but not as good with the CC as the output cable position. This told me that the output cable is a more critical position than the input cable with the Regen. Optimally, I would have both input and output cables to be superior USB cables, but if you just have one, try putting in the output position.
Here's my USB cable progression, each one sounding better than the previous (to my ears):
stock/generic < Belkin Gold < Audioquest Carbon < Black cat silver starlight < Curious Cable