Al, you are correct, when I moved into my new home in SC, I plugged each of my ROwland M925 monos into a dedicated 20A circuit, with a third circuit used for my line-level devices.
At first blush, I did detect a certain amount of hardness in the overall tembre. Within 3 to 4 weeks the hardness tapered off gradually and the tembre bloomed, and eventually it very much surpassed what the system was able to deliver in my previous home, where I had one dedicated circuit plus one shared line.
I should point out though, that my equipment had been in storage for six months between the old set up and the new one. So, it is possible that some of the initial anomalies and subsequent settling had to do with the electronic having regressed, and then re-broken in.
Guido