@faustuss You make an excellent point and raise a valid concern. For over 45 years I have wanted a dedicated line for my stereo after taking an Audio Physics class in college. I was either not in a position to afford it, or the line was an inconvenience, or both.
When we moved a few months ago I thought it would be nice to have a dedicated line, but it was a low priority with all the other challenges and expenses associated with moving. We were adding two 50A lines for the kiln and hot tub, so I asked the electrician about a dedicated IG 20A line and he said where I wanted it would be relatively easy, but I still was not convinced to do it. Then the wide voltage swings occurred multiple times. Over time my electrician identified multiple issues. The first was one he was aware of with the utility company (hopefully corrected although the neighborhood had another power outage this AM).
The second was the quality of some of the electrical lines in the house. We had to have the kitchen completely rewired to bring it up to code. The line that I wanted upgraded was questionable so the electrician thought it was a good idea to replace it considering the all the stereo equipment. He did not think the 20A was needed, but the cost between running a 20A and a 15A was minimal. He also did not think the isolated ground was necessary, but I insisted. As he was looking at installing it he discovered the grounding for the whole house was not adequate, so to have an IG for the 20A line the whole house grounding would need to be brought up to code. He felt this was absolutely necessary, but would not have been identified without the request for the 20A IG request.
I believe my Panamax power conditioner was near the end of it's useful life. While researching power conditioners I was initially drawn to the PS Audio Power Plant 12 or 20. That led me to look at other power conditioners. Ultimately other units appeared to meet my needs better. The Shunyata Delta-X is perhaps overkill, but I like to splurge from time to time too. The Furman 2400 is my safety net. The Delta-X does not have enough outlets for my system, plus the voltage regulation may or may not impact the output of the Delta -X. I will experiment with the Delta-X through the Furman (original plan with both), and separate (with power upgrades from the utility company and my electrician). The deal on the Delta-X and the two Alpha-X cables while not cheap does fall into my 'thrifty', as in big discounts.
Finally, as @faustuss pointed out the 20A line provides plenty, if not excessive, headroom for my system. Perhaps I will upgrade the power amp in the future? Doubt it, but never say never. The Furman 2400 requires a 20A plug and the Shunyata specifies one.
In this hobby everything is relative. I am enjoying it. Thanks for the input. It allowed me an opportunity to put all my reasons for the upgrade in one place.