Joe is really spot on, everything is relative to the decade. I remember being really excited to buy my first Kenwood home theater receiver that advertised 120W per channel, but it completely ran out of gas compared to a Denon DRA-400 that I also happened to own but was rated at 40W. After that I started paying a lot more attention to what things weighed!
For vintage amps, I like to post a before and after of a Pioneer 9500's frequency response into a test woofer before and after recapping:
View attachment 177236
View attachment 177237
It's important not to evaluate something that's more than 20 years old unless it has new power supply caps!
Weight seems to be a reasonably valid spec for an AB amp. Probably more informative than some specs published.
But yea, some of them were and are still great. There is a reason an Aragon, Krell, Levenson, Nak P7, still go for big money. An Adcom POOGED? Hafler POOGED? My own amp flat blows the doors off quite a few current amps. I mean not even close. I can't say what sound it has except it does not accentuate over sibilant vocals, top-hats, or other sources of "digital glare" whatever that is. Smooth. Don't feel like it is missing anything. Would the best of today do that to mine? Half of me wants to know and if so I would buy it. The other half says mine is darn good and I am a cheap SOB.
BUT again, we have some newer amps that seem to "have no sound" so would I pay $3000 for a pair of vintage ML monoblocks when I can buy a Benchmark for same? Can they beat a C298? Readers would like to know.
I do know the only time I heard a "stereo" I could almost believe was live was years ago in Boulder Sound Gallery. It was a half-track tape played on an A-77, feeding ML pre and amps into the first generation B&W 801. Solo upright bass being bowed and I think it was direct mic into that deck. Almost real. Really that good. The best I have heard since has been nice, but not real. I would hope we have made progress in over 40 years.