a commercial Hi-end amplifier with similar tube mounting plates -I’m sure I’ve seen more similar commercial
That looks like a typical chinese made amp.
"Hi end, commercial & Chinese", = oxymoron.
I don't understand why people don't look at historical amps.
Eico, Scott, Dynaco, Leak, Quad give you a perfect idea of proper practice, or where they decide to cramp it.
Scott insisted on jamming it all inside a wooden cabinet, which gets way too hot.
That with the 4 x 7591stuffed in there still managed to get some brilliant OPT but sacrificed to an undersized PSU, and way too much heat.
If you want the best of the best example using multiple KT88, take a look at a HIWATT guitar amp, esp the 200W and 400W versions (real=300W).
Not only were they uber-powerful, but they run the stuff on the limit, and their fantastic wiring quality was a lesson to practically every serious amp builder in the world, and has never been bettered.
I don't understand this fixation from looking at "hi end" modern amps, they are mostly a pile of crap, and rarely perform even close to their claimed figures.