The problem with Vintage gear is that there is no generalization that is useful to be made...
I dont give a damn about general opinions about vintage...There is too much products and too much possibilities to made general dogmas ...
And no, i dont buy mine for the look or for nostalgia...Only S.Q. motivated me... And low price..
The only reason for me to buy vintage is : HIGH Sound quality / low price ratio ... In some case for sure...
My two Sansui had so many positive factors about them:
The Sansui AU 7700 had a power amplifier separable from the pré-amplification...
An insane numbers of controls ( all of high quality design say my repairman)
i pay it 100 bucks and another 100 bucks to be reconditioned by a very well knowleadgeable guy...
The other Sansui AU alpha 607 i i paid 300 bucks is so good that beating it will cost way, way more...I used it for my K340 ...It work with a better low noise floor which is absolutely necessary with the K340...
But these two amplifiers can be replaced by contemporary improving upgrade at higher cost for sure but they can be replaced...
But no modern amplifier had all the versatile set of functions of the Sansui AU 7700... NONE...
They can be replaced anyway, nevermind their price or even their advantages...
But there is vintage and vintage...
Nobody can replace a technology so good that the sound quality is UNIQUE... I did not say BETTER over 5,000 bucks headphone here ,.. i said UNIQUE compared to anything ...
No contemporary headphone is like the AKG K340... NONE...
The only successful hybrid ( dynamic and electroacoustic cell with a croosover at 4KHZ) in history, and an headphone integrating in it a dual acoustic chamber created by an array of 5 tuned Helmholtz resonators Patented by Dr. Gorike...
The guy at Kennerton headphone company said to me they tried to create an hybrid but it is too complex to design well , and too costly to research, and too costly to assemble for a profit and they quit this almost impossible commercial task...
For AKG too it was too complex and too costly... But Dr, Gorike was one of the two founders of the company and a physicist and acoustician... He decided that this K340 could be done and it would be their FLAGSHIP in 1978...Nobody said to him it is too costly and too complex to manufacture at low cost...He was the boss...
They did it for the sake of an ACOUSTIC problem and challenge...it stayed their flaghip for some years but they decided once the challenge completed that it is better commercially to revolutionize the headphone market again but with a less costly product to assemble...it was the AKG K1000... ( The k340 with its electroacoustic cell give a perfect high range but thanks to the dynamic cell and resonators give bass only subwoofer can give then the K1000 dont interested me at all , add to that that the soundfield of the k340 is speaker like out of the head and is COMPLETELY recording dependant for the soundstage dimensions.)
Now think about that: this K340 vintage i paid 100 bucks and which i optimized with 6 months of listening experiments is now so good, all my otger 9 headphones are trash for me compared to it, i never use them ...( two Stax, 5 dynamics, 2 planar)
More than that no headphones at any price can give this soundfield which is completely different from any other headphone... is it better ?Not necessarily. But it will take a very costly headphone if you want to beat the K340 on ALL acoustical factors not only on one... This k340 is irreplaceable by anything...Especially for his price used...
After the lost of my dedicated room i will be in depression if i did not work with it...
I do not recommend it to newcomers though because it is too difficult to figure out how it work and with which components to pair it and which modifications will improve it... it is the most difficult headphone to drive... And very picky... And the design is 45 years old now and fragile...
Conclusion : There is Vintage, and there is another vintage etc etc...
No general rule here, only specific case...
But my 600 bucks system is very good i dont need upgrade ... Even if there is alway possible upgrade the K340 will not be the first component to be upgrade i really want to do it... I dont need i listen music in ectasy... Sound do not bother me at all...
Now alas! in much case the price are too higher... good deal are rare...I bought mine many years ago, 5 years for the headphone, and much more for the Sansui.. And with vintage there is reparation or conditioning fees, and risks... Then.... I was lucky...