Power regenerator vs conditioner

I use PS Audio older Power Plant Premier. I have Purist power cord from the wall to it and better Purist from the regenerator to power amp. Still, sound quality varies dramatically depending on how bad the incoming current is. If I plug the amp directly into the wall, the system is unlistenable most of the time, the wall current is that bad. So yes, regenerator helps a lot but it's not really good enough. Maybe newer PS Audio regenerators are much better, I don't know. Anyone compared ?
My SS amp is 80 watt/ch. Tape deck cares less about the current than any other piece of equipment in my set up, turntable and power amp care most.

If the goal is to improve the sound quality (soundstage, detail, dynamics, etc) and the issue is "noisy" AC, it would seem to me that a power regenerator such as PS Audio P15 would be far superior to a "conditioner" such as a Shunyata Denali or Hydra or Triton.  Is this correct?

No, it is not correct. The first part of the question you ask, "if the goal is to improve sound quality (soundstage, detail, dynamics, etc)" is fine. That is indeed the goal. But then you combine that with, "and the issue is..." as if you know what the issue is. If you know what the issue is then go build your own! The problem is precisely that no one really knows what the issue is! 

That is why tvad is correct, all you can do is go by how they sound. Either listen for yourself or read a lot of reviews and go by what people hear. Not what they measure! We don't know enough to go by measurement. Not even close! Or else this would all be so very simple. Go by what people hear only and you will be fine. 

Give you an example. Part of what contributes to the improved sound quality you want is nothing more than a good steady stream of power. Music sucks power very unevenly with lots of transient spikes. Every time this happens there is a very brief voltage drop. You can improve this with something as simple as a large cap. I had a friend one time scored one at Boeing Surplus, brought it over, and it was scary as hell but we hooked it up and you would be shocked (heh) at the improvement. No, seriously. It was a nice improvement.  

You could also connect just about any decent size transformer. People call them isolation transformers. They are ALL isolation transformers! It's just the way they work. It is very hard to make a transformer that is linear at high frequences. A lot of line noise is RF, that is all high frequency, and so they all isolate from RF to some degree. All of em. So that is another way. 

I can keep going like this with examples all day long. Bottom line, all these various factors contribute, but no one understands exactly how much of which is best, and so all you can do is go and listen. You will see.

I now feel very lucky to have scored Shunyata Triton/Thyphon.
They retailed for $9K each. Not unlike their current top line unit and top power chord. But the T/T are two full size components. The Triton is plugged into the Thyphon and they work together. The improvement in SQ is nothing short of spectacular! Akin to the perceived value of my system doubling. No exaggeration!
Shunyata is one of the few Audio companies who have a division that supplies Science, Medical, and Military. And have many, many patents.

For $18k custom batteries that would power the entire system would be preferable. Anyone takes this kind of order ? But there are no perfect solutions, batteries would give some noise too and dynamics might be compromised a little. I mean great custom battery with the right response and discharge curve.

The most quoted showdown around here the top PS PowerPlant edge out the top AQ Niagra.
Both bettered by expensive power cords.
Whatever butters your biscuit. Ask Mikey Fremer which technology works better.