@Nils I agree with your findings, to the extent that an external observer would say I have become a bit obsessed about DC supply quality to every part of my system, including ISP modem and router.
I found further conditioning of the output of decent LPS's with either iFi DC Purifiers or DXPWR's helps further - basically the lower the noise on the DC the better, as long as your supply still presents a low input impedance to the device you are powering. The number of boxes proliferated, but definitely helped sound quality here.
Incidentally, I also use iFi AC Purifiers on my dedicated mains supplies to the different sides of my system (I have two 30A lines and two 20A lines dedicated to hifi) again with very obvious benefits to sound quality.
Weird really, I don't consider myself at all a power 'nerd' but have been pushed into the territory by seeking sound quality improvements, I found it really does make a significant difference on every component! Same with shielding from WiFi.
All the best!