The "golden age" of audio reproduction is universally considered to
have been somewhere between 1953 and 1971.

Reflecting further, I think I may have been off a little. Perhaps 1983 to
1993. In the early 90's, Sony made two channel receivers with toroidal
transformers. I have heard one, and been very impressed. I myself own a
Nakamichi TA-4A, which has a Nelson Pass quasi Class A output stage. It
seems fully on a par with separates, but requires very careful ventilation,
perhaps a fan, if used with full size speakers.

With respect to the dates you quote, it may be accurate in terms of
aspirations, but not, in my opinion, in terms of results.

As far as receivers, true, but no one bought receivers or even
integrateds in those days if they were serious.

The best amps and preamps of the day-the McIntosh MC240 and 275 amps,
C22 pre, MR67 and 71 tuners, the Marantz 7C pre and 5 and 8B amplifiers
(notice I'm not mentioning the overrated 10B tuner, and the Marantz 7
and Mac C22 being nearly identical)- are still, in blueprinted stock
form, better than pretty good sonically-in particular, only handcrafted
two stage passive phono sections custom-matched to specific cartridges
by very determined DIYers can substantially best the Marantz 7C, and
commercial preamps by Mark Levinson, Jeff Rowland, ARC, c-j, and others
of similar pricing often fail to equal this unit or do so but little or
no better. Half a century on that's no small thing!

And commercially available output transformers, the core component of
the tube power amp, are not substantially improved in performance from
when JFK was President, although the insulation materials certainly can
be. Solid state amps are much better, but the fact people still build
late-70s Nelson Pass circuits avidly says a lot.