Well, it seems there is still hope
I added the UpTone Audio JS-2 and UltraCap LPS-1 PSU combo to feed my Jcat Femto USB card (it was powered internally by not-so-clean power from the MoBo before) and now my PC server and Aurender W20 are neck to neck. I have been switching back and forth the whole day, and I cannot say I have a preference for one or the other. They are very, very close. I would not be able to tell them apart in a blind test.
Which is a great sign, as I still have the Core Mode and HQ Player up my sleeve to try (I've been using the Jriver 21 in bitperfect (Bitstreaming) mode playing DSD files vs the Aurender).
But still - if you consider how many boxes I have now (the server itself + 4 (FOUR !) outboard PSUs + Synology 1815plus NAS) - the Aurender W20 is still a great all-in-one solution for those who have the funds and are not into the geek stuff.
Honestly, if you have the money and would rather spend your time listening to music than solving the hardware issues, the Aurender W20 is still way to go.