Thanks, sub, for that quote from classicaudio. That really nails it for receivers.
I believe that amplifiers reached maturity in the early 80s, and several brands made excellent separates. I have several amps, and the Soundcraftsmen could have been made in 1979, but are probably from the 80s. My Yamaha amps are from 1982-84 and 1984-85, & the Denon is from 1986-88.
Preamps, though, have really benefitted from better "pieces-parts", and I have gone to mid-90s preamps, the Luxman C-383 & the Yamaha CX-2.
The source + preamp + speakers really determine the overall sound of a system--provided the amplifier is working as intended within its performance envelope.
2 of my receivers are pure vintage, the amazing Concept 16.5 and the Nikko NR-1015, and one that is near vintage, from 1981-83 and carried on with massive power rated at 150 wpc and 3dB headroom.