Amps from the 1980's -- What gear holds up sonically? Reliably?

Equipment I or my close friends have still in use .... Amber 70 amp (original condition), HK Citation 11 (original condition), Teac 7040 high speed two track tape deck (original condition), Teac 4070 consumer tape deck (just had minor servicing, first since I bought it in 1970), Audio Research SP6-B (in daily use from 1980 untill I sold it in 2007), Audio Research D90 (in daily use from 1980 until I sold it in 2007), Thiel 3.5 speakers (four, in use since 1989), Thiel 2 2's (two, in use since 1995), Audionics Bt-2 preamp and CC-2 power amp (I've owned six at one time or another in original condition, no problems with any an all sounded great although not with exceptionally low noise or transparency.  BTW, the CC-2 was THE FIRST low TIM amplifier).
Koss Pro 4aa headphones.  Heil AMT-1 speakers (with woofer suspension replacment).  Counterpoint SA-1000.

This is all gear that is up to modern standards and operating in substantially good systems.  Hope this helps.

Forgot to add .... whether or not the gear has been in frequent use is important to maintaining the condition of passive (and some other) parts. Perhaps as much or more as "brand".

Seriously, nobody's bringing up McIntosh ????

I just rebuilt a MC2300 for a friend (can't do what we did for $$$, only for friends). Compared it to our Aurion(tm) with nCores - now the MC2300 isn't a Constellation - but I was surprised how good the sound quality is. Those OPTs Mac held onto must have something to do with it. Stable as hell, very musical amp. Circuit design is as basic as you can get, but this amp has held up for almost 50 years! Who can say that now?

I’m the original owner of a beloved SAE 2200 amp bought in 1977 that is still in use. In 2001 I paid the original designer James Bongioro to completely upgrade it. Every capacitor got replaced with poly & premium electrolytics. He replaced all the semiconductors (diodes, transistors) except the matched input transistors which he said were working well and had no better modern alternatives. The output power protection circuit was removed. And the final upgrade was his addition of an op amp servo bias circuit board that was not present in the original SAE design. He used an Ampzilla servo bias circuit board. Boy did he boost the bias voltage over the original factory set level, too! The unit now runs about 50% hotter (and sweeter) than it did all those years before 2001.

Recently I’ve added an Ayre AX-5 Twenty amp for daily use. But I still have the SAE 2200 hooked up. I’ve auditioned many solid state mid-high amps over the years and until I heard the Ayre, none were more musical than my upgraded SAE. Certainly nothing within an order of magnitude above the $400 paid to James for the upgrade.

James Bongiorno, a "pioneer of audio", passed on in 2013, sad to say. http://forum.audiogon.com/discussions/death-of-jim-bongiorno

I've had several models of Sumo amps through here in the past 20 years, of them 3 Nine Class A's including the prototype. None of them needed recapping (per James Bongiorno who I befriended in '98) and all of them sounded great. We did mod the Nines to a newer opamp and IEC socket but I also had an Andromeda, a NOS Gold, and a NOS Power, the Power especially took my breath away. I still have the silver-faced rackmount Nine plus a Rowland Model 5, a ML no.336, and a Bedini 250/250 working perfectly now as when they left the factories. Only my Mac 2105, probably 70's, needed new power supply caps (oversized ones definitely gave me better bottom end). I also use a Nak 420 power amp in my studio from that era. There's also a Yamaha P2200, BGW 750D, QSC USA 400, an Audionics PZ3, and a hunkering Crest 4001 in the garage, all still work fine. The only other amp I had to replace caps in was a Harmon Kardon Q50A from 1964, rather older than these. Quicksilver caps were a huge upgrade but we also bypassed all the junk stages (tone, filters, blend) and the thing sounds awesome. Only a Merrill Veritas monoblock pair ( here for review, $12K) exceeded these but I didn't have the Levinson then which is my daily driver. I can't believe some people feel all amps sound alike (AES!) but then I hear cable differences too, so sue me. ABX is deeply flawed. Go with your ears...after a reference check multiple times. Blah, blah...