Grainger49, you and I have gone down similar paths, though with different results. I lived with a Powerwedge for about 20 years and loved it. Realizing the Paramounts needed lower voltage input, I decided to buy a PS Audio PPP. I thought this would be a more elegant solution than adding a variac. When I got everything hooked up, the voltage reading on the PPP was 121 VAC. The outlet was measuring 128VAC, though that reading only lasted a week and I haven't measured that high since. I called PS Audio and they indicated that the PPP will adjust voltage by up to 7 volts. The PPP can be adjusted to to increase the voltage step down, but at the same time putting more stress on the unit. After I got the PPP adjusted, I settled in for some listening. I heard most of the same things you did with your P300. I was especially taken with the black background. What I never got used to was the hardness in the highs, which never went away after 100 hrs of break in. So, I sold the PPP and bought a used Audio Magic Stealth XXX for power cleaning (big improvement) and us a variac for voltage control. I leave my multimeter attached to the variac so I can get the desired voltage each time I turn it on. I usually set it to 115VAC because it sounds better there. I have never observed the voltage changing during a listening session.
The P300 is an intriguing option. A lot of people like them better than the PPP, and there are always a few for sale on AudioGon. Monarchy still makes a regenerator, but it only handles 100 watts input. One of the neat things about the Monarchy is that you can adjust output frequency and voltage (100-120), though the low power probably makes it more suitable for front end components There are the Pure Power regens as well.