I heard P15 a couple times this past year in my system. I thought I had decent mains power quality, but it was actually 4% THD with typical peak clipping. I've tried Equitech balanced and lots of passive filters over the years with either negative results or barely noticeable. I liked the equitech on my tube amps which benefited from the equitech's huge magnetic reservoir, but SS amps with relatively large transformers didn't noticeably benefit. But the P15 was a game changer, obvious and significant improvements on the amps and DACs.
I can't imagine how anyone would need the P20, as the P15 is a 90 pound monster to move. I'm thinking about the P12, it's more than enough for me.
I think you'll like it!