I am a fan of vintage 70's gear and an owner of Realistic receiver of 22wpc which drive decent pair of British speakers. Sound melts my soul every time I use it and never put volume above 40%, I love it unconditionaly, but recently had a browse through ebay and found a few with more than 100wpc. I have never had a chance to listen to any amp/receiver from that era with such great power as these from list above and have an honest question why are these powerful receivers such desirable. What is the point if most of listening oscilating below 10 watts output and the prices are significant?
I own several amps and mono amps that have output more than I need — even for the vintage speakers I use in a small room. I bought them used because the price was right and they were/are excellent machines. I think that I can use use them to advantage because my speakers are sealed boxes with huge drivers and they require power — and they get it!
To answer your question: in the late 70's, through the 80's and into the 90's, many (not all by any means) speaker designs required lots of power. IMHO most if not all of them required no more than 100 Watt amps and many were OK with 50. Electro-static designs were reportedly requiring tons of power. That being said, my Dynaco ST-70 at 35 watts per side drove a big pair of electro-static speakers to some of the best audio I have ever had over all the decades. Mind you, when I took the Dyna apart I found evidence of ... er ... stress:scratch2:
It keeps being said that modern speakers comfortably accommodate much lower amp output. We are now entering a new era and have been doing so for some time. IMHO, the monster amps are almost dinosaurs. I say 'almost' because if you own speakers that require lots and lots of power, you may need the 'dino amp'. You might get away with less — as I have in the past, but with dino speakers it is best to have at least the recommended power as well as having some juice in reserve. Take a 70-80's system — amp/speaker combination: Tchaikovsky's 1812 with cannon should rattle the ice cubes around in your scotch tumbler. But on the other hand, with very efficient speakers powered by a flea tube amp, I have felt and heard the same thing. However, a certain irony came to light: the amp cost a fraction of what the speakers were worth on the market at that time. A decade on, you might do better — I dunno.
Some of these old dinos were just plain excellent electronics — bragging points aside. They are worth collecting and restoring if that is worth your interest.
If I were to start over again as a youngster in audio, I'd be into very sensitive speakers, and either small tube amps or "T" or class "D" amps. In fact, as old as I am, I may do the revision anyway — eventually.
Years ago, I could actually see how much music I was playing by looking at my electric bill. If you think I am kidding, audio friends said the same thing. Today you should be able to put together a system that is powered by a DC supply of 12 - 24 Volts and consuming no more than 2 watts in total. (I hope I have those numbers in the ball park — could be less!)
Final word: have nothing against the 'T-Rex' of amps if they are euphonic. I have some amps that will put out 150 at 4 ohms — less at 8 Ohms. One of them (a huge Sansui) is brilliant, and nothing like anything else I have ever heard in my rooms. But I do not for a minute doubt that today's power misers can match it if the engineering is equal and the speakers match the amp.