Sold Dynaco in the late 60's. My boss told me that folks were saying their old tube Dyna stuff sounded better than the PAT-4/ST-120 I wanted to order (and did). That was clearly crazy. Took me probably 5 years to hear enough tired old traded in ST-70's to realize he was tellin me the truth.
I seem to remember the "corrected" power output of a stereo 70 was 28 WPC at rated distortion 20-20kHz ?
Today -they are going to be a project rather than just a simple retube.
Starting in the late '60s, and by the '70s, the big mass market was in acoustic suspension type speakers. Small package, cheap to manufacture, and fairly even sound from top to bottom. Many were 4 ohm, and not too sensitive. AR3a, and so forth. I suspect that an ST-70 would be a good match, not strictly for power, but because of soft clipping tubes. But I'm just guessing; the AR thing was not my thing, and they never got my dollars.
The FTC schedule was not helpful for tube amps. The rule certainly did away with ridiculous claims (IHF power, peak power, music power...), so that was good, I guess.
By the early '70s transistors amps became more reliable. Everyone wanted a transistor amp. If you had a lot of dollars and wanted power you could get a Crown DC-300, at 150 per channel. Shortly thereafter, Bob Carver started selling his 700 watt (350/ch) monster amplifier, mainly to cope with the then power requirements of low sensitivity speakers. The AR LST could take 1000 watts for short bursts. Bob wrote an article about it, in
Audio magazine, which still makes interesting reading. Prior to that time, 60 solid state watts per channel was considered a lot. In another few years Japanese were selling receivers with more watts than the Crown, and almost as much as the Phase Linear.
I advise everyone to build (refurb) a Dynakit. Not because of sound. But because it's fun. And we need more fun and enjoyment in the world.