Power Distributors: Shunyata Delta-X, AudioQuest Niagara 5000, and PS Audio PowerPlant 12

I would drop that question into and AI. It does a great job of characterizing your problem and how each of these units are designed to do different things. Here's a very short summary:

Given wide voltage swings (≈98–145V), the core issue is voltage stability, not just noise filtering, so a true regulator like the Furman P-2400 AR is the foundation; downstream units like the Shunyata Denali Delta-X and AudioQuest Niagara 5000 primarily provide passive conditioning and distribution (useful once voltage is stable), while the PS Audio PowerPlant 12 also regulates but would be redundant and potentially current-limiting in this setup; the optimal approach is to use the Furman for regulation, run high-current gear like the Pass Labs XA-25 directly from it, and use a conditioner (Niagara or Delta-X) only for front-end components, with premium cables like the Shunyata Alpha-X XC being optional and secondary to stabilizing the incoming power.

Add the Furman Reference 15i (or 20i) to your list. 

@zlone When I started this research the P12 and the P20 were at the top of my list. As I dug into the research, including speaking directly with PS Audio it became evident that the P20 would not be able handle the wide swings indefinitely. While I believe that the utility company and my electrician will be able to narrow the voltage I was concerned it would be pushing the unit to the limit. Putting a strong voltage regulator in the line first would allow me to run the high demand equipment like the Pass XA25. I did reach out to Pass Labs and they were adamant that the XA25 would be limited by the P20 and that the line would need voltage protection. They actually convinced me to get something like the Furman as a first line of defense. 

@ghdprentice Thanks. That is consistent with what the experts also say. Do you have any experience with the Niagara or the Delta-X. I have narrowed my choices by eliminating the P12.

As already articulated, the huge voltage swing is your biggest issue, not only for your stereo system, but, also for your home appliances... Decades ago, like the 50's and 60's applicances were engineered to handle voltages down to 95 Volts, but, no more... Modern appliances are all about cost cutting and efficiency.  The windows of operation for longevity are narrow.   Personally, I would concentrate more on addressing that... As a comparaison, the voltage swing at my house is 115V to 120 Volts.

That makes a lot of sense, good that you checked with PS Audio. I use a P15 with good results, but I have pretty stable voltage. And I agree with Pass, I ran my amp through the P15 for a month or so and switching to the wall was an improvement.

Good luck sorting this out.