A couple of years back I bought a Power Plant P5 on eBay, and had them ship it to PS Audio to confirm that everything was fine. After checking it out, they shipped it on to me, and I tried it in my system. I discovered that my power amps sounded less lively and engaging with the P5 in the chain, so I sold that P5.
Later, someone commented that I was expecting too much of a P5, and that I should try a P12 or better. Consequently, I bought a used P12 and tested it with some of my power amps (all Class AB). It affected the performance in the exact same way. 
I figured it should work fine with my lower current devices, so I plugged in only my Denafrips Gaia DDC and Ferrum Hypsos power supply (feeding my Wandla DAC). At first it seemed like things were nicely cleaner, but after a while I realized that it was similarly stripping some of the the fun from the music. I kept it in the system for a week, thinking that I must be imaging things. Each time I played music it sounded very nice, but it never drew me in.
Yesterday evening, I replaced it with a good power bar (just 20A commercial receptacles, no filtering or surge suppression), and the sound immediately blossomed. There was more presence, energy, and engagement. It went from beautiful and polite background music to something more alive and demanding.
Perhaps it wasn’t quite as clean sounding, but that wasn’t obvious. It was definitely less demure. The most important indicator was the extended listening session, late into the night. That hasn’t happened since I injected the P12 in the a week ago.
I’m trying to figure out what’s going on. The P12 should have plenty of juice for these two front-end components. How could it change the character of the presentation so much? Could it be defective somehow? It seems to function correctly, but perhaps the capacitors are old. 
Do power plants need to be recapped regularly?
Does anyone have any insights?