Food for thought from Rob Watts himself:
“Actually my advice is that the supplied PSU is as good as a battery supply (based on my listening with my set-up -YMMV) - which gives the lowest amount of RF noise - and that LPS supplies is likely to sound worse, as they are often transparent to RF noise from the mains - the supplied switcher has RF filters. My advice is to try a USB
battery bank, and if it sounds identical to the supplied PSU, then don't bother "upgrading" with a LPS...
The hard bright sound is characteristic of more random RF noise entering your system, creating more noise floor modulation, which makes it sound brighter, and if bad, harder and grainy.”
I'm using a Hugo 2 and, to be perfectly frank, have found Rob's advice to be pretty spot on, saving me some dosh.