"all 6-string guitars were done with tube PAs modified for guitar use"
Awesome! Once you start messing around with tube amps, you can't stop. I've built two now (actually just got my second one working about an hour ago...
). When you build amps, you start listening to the sound so closely that you develop a very discriminating ear, I think. That's why I like your tone--it's warm and strong, clearly tube-generated.
Single-ended amps are SWEET for recording hard rock tones. They actually distort more than larger push-pull amps, I think. They don't sound too good clean, though.
"it's pretty low wattage (maybe 5-10?)."
What kind of output tube, and how many? 10 watts is a lot louder than 5.
"it's kind of a gamble when you buy them if they'll sound good for your needs."
You can change the sound easily with different coupling caps, a better speaker, different cathode and plate resistors, etc.
Rock on, man!!!