I haven't read every post in this thread, but as a long time owner of many tube amps (and purchaser of a Singlepower PPX3 Slam Extreme), I would like to add my $0.02.
1. The Singlepower products are, by industry standards, low volume, hand made products. There are plusses and minuses to this kind of product, but they are what they are. In my view, this type of operation is more rapidly affected, and affected to a greater absolute extent, by inflation than larger businesses or business with different business models. They have a much smaller margin for error in meeting their weekly payroll, monthly rent and other fixed costs.
2. Because it is basically a boutique operation, Singlepower will work with any product they have ever made. You get to talk to the guys who actually design and build the amps. Singlepower will fix any problems with their amps without arguing with the customer -- Singlepower is obsessed with customer satisfaction. I own other products made by other manufacturers that have the same attitude, but their names include Audio Research and McIntosh, and I can assure you that the price of their comparable approach to service and customer satisfaction is a heck of lot greater than at Singlepower.
It is frustrating to wait a long time to get an upgrade -- or even to purchase an amp -- but you have to remember you are dealing with a small company run by real people who, in the end, will take good care of you.
At least that has been my experience. Regards, James