Thank you so much for your reply regarding the single P20 vs the twin P15s, Paul. Sorry for withdrawing the photo - there’s a long story behind my journey to build my acoustically optimized listening room. Can I send you a PM?
[What’s the difference in the circuitry between the P15 and P20? The circuitry in each is new, isn’t it?
They are. Nothing’s different. Just one has a lot more of it than the other. The biggest sonic benefit of Power Plants is the active lowering of output impedance feeding the gear. The P20 has considerably lower output impedance than any product we’ve ever made.
Following up, a brand new P20 was delivered this past Tuesday (it is now Friday). Upon plug in there was a noticeable improvement in sound quality. Before the P20 was installed I had been listening to my system powered by my P10 for perhaps 3 or 4 hours. It took perhaps 1/2 hour to make the change. I am not sure how that much time affects judgement, but I hear an improvement in clarity in terms of delineation between notes and instruments across the entire audible spectrum. The difference is not subtle. And this is right out of the box. The P20 has been continuously powered ever since arrival and continues to impress although I cannot vouch that it is improving. My auditory memory is not good enough for that. On the other hand, there is no question that some very well recorded piano recordings, with which I am extremely familiar, offer ample proof that the P20 has made a very worthwhile improvement. There are some background effects such as bells, wood blocks, fingered drum beats and so on, on other recordings that stand out in sharp relief in a way that they never had before. The P20 performs above expectation.
Bill
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IF the P20 indeed has a significantly lower output impedance than even the P15, it’s certainly not evident through the specifications in the web pages, as they both are listed as being identical, at “< 0.005 ohms”. Paul, would PS Audio care to quantify the specifications more granularly / precisely? Perhaps if it’s a dynamic function of the output current, perhaps two ranges can be separately specified, for example: output impedance @ <1,000VA, and output impedance @ 1,000VA < 2,000VA, etc?
Whoops - mea culpa! I checked the website again for the specs, and it says <0.005 ohms for the P20, and <0.008 ohms for the P15. OK, so the P20’s output impedance is typically 3/8, or 38% lower. 
Compared to the P10’s spec of <0.015 ohms, the P20 and the P10’s output impedances are lower by 66% and 47%, respectively.
Or roughly speaking, in layman’s language, “more than half (for the P20)”, and “almost half (for the P15)”.
Previously, I was considering replacing my twin P10s with with either twin P15s or a single P20. I have managed to remove my component rack space (and financial) constraints, and therefore can now consider twin P20s. Exiting times ahead !
Yes, sorry for any confusion. They certainly are different and measure lower and those are conservative measurements.
Paul,
One more question before I leave you alone. Would there be any benefit to having a dedicated 20 amp circuit installed? What if I added a couple of subs? Current draw is hovering at <600 VA.
BTW, my wife and I were listening to Mel Torme backed by George Shearing on Concord Jazz (circa 1993), a well recorded vinyl record in near mint condition. She suddenly exclaimed how extraordinary it sounded. Although she has a good ear this sort of thing is rare from her. The P20 makes a very noticeable difference, no question.
Bill
Bill, this should shed some lights:
To nortonkp…
I am almost running the same set up as you on a new to me P-10. Except I have a BHK 250 and the M700 ss mono blocks with a pair of REL class D subs at 450 wpc each. So I am running substantially less power draw than you. However I managed trip my P-10 on over load 3 times yesterday. The first time it tripped I put my P5 back in and moved the M700, BHK pre, DS Dac, DMP all on it. Which it handled no problem at 40-50% load. It is amazing how efficient the M700 are with power consumption. Then the P10 tripped again so I moved one the subs direct to one of my dedicated circuits. Seems to be holding but I can’t believe the power requirements of the BHK 250. I am peaking at 100-120% load on the P10. Now I am volumed up to Max of what the room can handle at BHK pre volume of 45.
I wouldn’t stand a chance of reaching that volume with the 300 mono blocks.
Apparently I really need a P20.
Cugething I play my music at 45 or below as well. Cranked it up to 49 once or twice for rock drum solos. Sounds great but hurt my ears.
I originally had a P10 with my DS DAC, DMP, BHK Pre, BHK 250 and Paradigm 1000W subs. The P10 ran between 42% & 49% capacity depending on volume and music content. The BHK 300s bumped things up to between 47% and 55% capacity. I also have a 65” Sony LCD TV, Sony Blue ray and Cable box plugged into it. They are off when listening to music. When watching a movie my P10 would be over 60% capacity.
Finally, the P20 will make you system so much better. Some said spooky real. I’d say much more natural like a veil was lifted or a lense was removed. In a word, ‘amazing’ which is funny because I originally felt the same way about my P10! Paul mentioned the P20 has twice the output devices as a P10 / P15 so automotive analogy, if the P10 / P15 is a V6 the P20 is a V12. A reserve is always a good thing when it comes to power, alway.