Once again, I return to how radical a departure Arthur's posts are when discussing power in amplifiers.
Unfortunately, our posts are again dealing in the traditional means of trying to explain how the watts we measure in a tube amplifier versus a solid state amplifier still correlate in a 1 to 1 ratio. The point is, they don't. Well, at least, not in a useful way of the music / amplifier / loudspeaker relationship. As Arthur gave a glimpse of in such an utterly brilliant way in his initial post, tubes and transistors operate in VASTLY different ways. Like comparing an NFL running back coming through the hole on a play to a distance runner in a 10K event, both moving at 10 mph, living in a world where we use a steady state (linear, quadratic, or even cubic, etc.) measurement to compare them confuses the issue, and only delays us further from the questions and answers that will ultimately solve the puzzle.
Again, this is a question of calculus. Yet we're still attempting to shove it into an arithmetic / algebraic model. Sorry to say, but it just ain't gonna work. Until we come to grips with the fact that we need to operate under a completely different paradigm we're going to be splitting hairs on issues that bring us no closer to understanding.
Grant's question, "What's hotter, 85° in Miami, or 85° in Phoenix?" can get the dialogue back on track. Back in my days as a research chemist / material science engineer, I would use an analogous example in taking the first step in illustrating the difference between temperature and heat. When you open the 350 degree F oven you're baking a cake in, the air and metal oven racks / pans are obviously both at 350 degrees F. And while you are in no peril in putting your bare hand into the oven in contact with 350 degree air, you know not to grab the racks or pans which are at the same 350 degrees F without the protection of an oven mitt or potholder. Without going into the mathematics involved, the metal will transfer that 350 degrees F instantaneously into your flesh, the air does so in a much more gradual manner. In simple terms, that's the difference between temperature and heat.
What I'm getting at is we need to come up with the same type of "temperature versus heat" model when dealing with amplifier power. Then, we'll be capable of satisfying Unsound's relevant question.
The last thing I want to say is that we must also be on guard to not fall into the trap of trying to explain why some folks choose tube amplification as simply a matter of power. Power is but one piece in the puzzle.