In the early days of amps, long before wave soldering came to the industry, components were hand assembled on a circuit board. The amps were simple and sounded lovely! As electrical engineers entered the fray, circuits became more complex and economics entered the mass produced market. I get the sense that circuit boards entered the market right about the same time as cheaper components. I've read but never aligned with the hand-wired V circuit board difference. Case in point Soldano's SLO; a legendary sound that is circuit board based. At the same time, KBP810b has created many tasty hand-wired masterpieces. The difference, I believe, are the individual components. The less cost, generally, means higher tolerances allowing the sound to escape.
I believe in big transformers for many reasons. Empirically, every sweet amp I've played has big iron. I've had bad amps with big iron so it's not a sure-fire test.
KBP810 nailed the speaker factor. One might add the cab size too.
I've seen but never calculated amp wattage. There is a formula that takes into account the power in the circuit. I believe that is where the # of amps associated with a circuit originates. You can get a flavor of how many amperes from the power tube type. 6V6 ~ 7W, EL-84 ~ 9W, 6L6/5881 ~ 25W etc. There's only a 3db difference between a 50W and 100W amp. Don't sweat the petty stuff and don't pet the...