Call Upscale and ask them if the PL behaves like this when power tubes need replacing.
You can buy 2 matched pairs on Amazon for $89 a pair. 5 years is worth a replacement set.
"I apologize if I offended anyone with my modest problems. I settled on the Audiogon forum since it looked like it had the most knowledgeable and experienced members around. If it is strictly for much higher-end participants than myself, please let me know and I will move off."
Not at all. This site would be better if people like steakster moved off.
The cause of your issue can be anything in the chain from start to finish, including the source material, cables, seating location and the room itself. All you can do is replace one item at a time and listen to see if the problem has gone away. Do you have friends or a friendly dealer, that can loan you gear to eliminate each piece in your system?
I would start with the speakers, but I wouldn’t be shocked if it turned out to be the room.