My opinion is it sort of ended unexplainably abruptly when the Yen-$ values changed, the Behemoths became 40-50+ lb,
ate up appreciable shelf space, digital chips and memory got cheap, the Accounting Dept. won the war on the Engineers,
BPC came into vogue which were 1/2 the size and "could do the same thing", crammed more chip-type stuff under the hood, lost the point to point wiring, massive caps and weighted flywheel analog tuners,
and the concept of the "seperates" weren't any longer limited to Pugeot driving, tweed jacketed college Professors and GI's.
What was a Pioneer SA-80 amp by 1983, became the unibody chasis Pioneer SA-950 I have in the bedroom rack that boasts 70wpc
and is "decent", sound nothing alike.
I think the Concept 16.5 (Technics i think?) was the last giant receiver I saw at Pennys or Wards or Sears where most people shopped.
Sounds By Dave on Mangrove Ave., Chico, Ca has been there since the early 70's and was one of the few places in the NorCal countryside that carried and sound-roomed the really good stuff none of the working stiffs could shell out thousands for.
And I think the whole "Wife Factor" and 80's "modernizing" had people settling for the all in 1 formula Bose Acoustimass and a hundred others do to this day,
In those days of "new and sensationally light" BPC never really went out of style.
That being known, is why Grandpa's console system still sounded better than any the new stuff anybody had
and why I'm listening to a Jimi disc now just for its amp section of a 1978 Luxman R-1120.
Nothing in the 120watt league i;ve run across so far bests it for sheer great full sound.