A friend in TN got a PS Audio for a nice price, used I'm sure. He is a very critical listener, lower volumes to the point of me needing more volume just to hear it. His rig is better stuff including some highly modded bottlehead pieces and he says it makes a very noticeable difference for the better. I haven't heard it yet but I trust what he says.
The ac line is full of junk and some of it gets into the audio/motor controls and on some rigs with some hearing folks can appreciate the use of good clean power from a regen unit. I don't need measurements, listening tests are good enough. We don't know how to measure everything.