I tried a PS20 in my system for 3 weeks ( brand new) from a friend who was moving her system so I “broke in “ for her. I didn’t feel any “darker” nor “quieter” background as anticipated, but I felt the sound stage (left/right) was slightly compressed and less airy.
I eventually tried an Audience aR6 T4 with my same set up ( from a friend who had the unit broken in for over 1000 hours) and I found no such compression but also no audible improvement. I think my electricity from mains is clean and stable so it’s not much of benefits in my case
However I do hear significant difference if I swop my power cables (from stock to a $300 cable , and from a $300 to a $1500 Siltech or Transparent Ref) so I would recommend to invest in power cables before buying a conditioner / regen