The Gustard C16 external clock has an OCXO with its own power supply. The R26 has a crystal but not at the level of an OCXO, and it's rare to find a DAC with a separate power supply for the clock. That's part of the benefit of an external clock.
I may have changed my mind. You should probably ignore me because I keep changing it, but I listened to another DAC this weekend (the Denafrips Terminator 1), and tried another USB cable between my Aurender and each of my DAC options. I also considered that whatever I do I'll probably have this technician friend (Igor in New Jersey) modify the DAC, and in the case of the PS Audio he can do the well-known transformer and VOCM mods, which will probably increase the resale value as it's well regarded. I decided that the PS Audio has many strengths (such as faithful/beautiful timbre and musicality) and its only weakness is a bit lacking in oomph and resolution compared to the Denafrips or my previous DAC, the modified X20 pro. Well, Igor can fix that. The R26 and Denafrips had more weaknesses with no guarantee they can be fixed. So I think the winner at this point is the PS Audio! And off to the shop to get the transformer and VOCM mod, plus a power supply component upgrade. Anyway that's the plan. I keep changing it, but I'll know for sure at least by the time the R26 has to be returned to Amazon.