Can a Amp be "timeless" and compete with todays amps?

And then, of course, there exists the prospect of overthinking things until.....

I second @lancelock with the vintage theater amplifiers. I have the little brother of the 1570B, the Ampex 6516 monitor amplifier, that was used to master the soundtracks of movies. Of course, it needed heavy bringing up to date to be used as a stereo amplifier, but all that is largely cosmetic as we are talking about adding modern connectors, and also about taking out the first gain stage (as the input was tape level.)

Mine had seen extra heavy duty in a movie theatre for decades, so a nice tune-up was already in demand. Not because of the heavy use (which it can easily take, as it was designed to be operated 10h a day, every day, for decades), but simply because of the age.

Compared to the 1950s we have drastically better capacitor technology, and a LOT can be done to optimize the internal wiring.

Few other mods done, which are modifications and not just "oil change": power tubes running in triode mode, separate filament transformer, the C input supply changed to CLC input, feedback loop drastically reduced (and then fully removed).

For those measurement savvy, I measured it with the minimal feedback (less than 1dB), at full power output (20W) the low extension was -1dB at 10Hz. I have not re-measured after taking ou the NFB completely, but I can report that the sound is way more dynamic, live, and bass much more 3D and grabbing than with it.

Now, back to the sound quality....

It's simply astonishing. It is as emotional, pure and human as the best examples of SET amplifiers are. They have produced the MOST LIFELIKE violin reproduction I ever heard from a stereo. Well, they clock the only instance a violin felt real from recording, in any system ever. (That is was not "close" or "almost", but the real deal.) That says a lot, as even most ultra high end systems reproduce violins in cat major or flat mouse E sharp, or plastic being shredded by sharp steel A keys...

So, it's a rare form from any amplifier of any age to do the most basic form of justice to violins. The venerable Ampex excels at it. Yet, not just that... I can listen to Karyyn - Jaina or Billie Eilish When I was older, and feel as if I'm transported to another reality... these songs contain high levels of subsonic information, and these babies can deliver it like nothing I ever heard. (Well, that might show my narrow-experence with HE systems boasting sub-20Hz provess... to tell the truth, we, audiophiles never listen to such material in our audio get togethers, so who knows really.)

So yes, I think "vintage" amplifiers are well and truly deserving of our attention, whether you are an UBER-fidelity fan (for life-like violin reproduction), or a hard-core rave party addict who wants to feel the marrow moving inside his bones (wants more than just a kick-in-the-chest...) 

Apologies if I duplicate other’s comments.

I think the simplest designs with solid components, whatever their strengths or weaknesses, have longevity, whatever your judgements are of their fundamental architecture or their particular performance. More complicated ones compete with successors’ evolutionary tweaks.

The other issue is that everything ages. There can be a multitude of performance changes that result from that, more or less amenable to intelligent maintenance.

OP, what exactly would be the problem if it WERE a hotrod job?  If you use "upgrade parts" [a relative term, I acknowledge], maybe you end up w/a BETTER sound that what it was originally...I say this because I am using an OLD Sansui integrated, slightly hotrodded [by someone else], driving some old Pioneers that are majorly hotrodded [by me].   WAY better sound; I sit and shake my head in wonder every time I listen to it.

But go w/whatever you like, obviously ~ just saying that ruling out upgrading something [like caps] might be your sonic loss>>>>>

I happen to have lots of vintage equipment and 10 integrated SS amps and 4 tube amps.I don't buy anything new.I like to find vintage equipment. I can't afford the new stuff.