Are "vintage" DAC's worthwhile, or is this a tech that does not age well


Hello,
whether it’s worth looking into old dac such as
Spectral SDR 2000,
Mark Levinson No.35 (36)
or so Sonic Frontiers Sfd-2 Mk2 DAC.

Digital audio is the fasted moving, now improving category out there
Because to this day they have no usb connection or other options.
But is it necessary?
Or is it better to still focus on a truly time-tested sound?

(sorry for my English)
128x128miglos
Any R2R Dacs will sound good.
I like the Holo Spring 
Wadia 64.4
Sonic Frontier SFD Mk3.
I haven’t heard Denafrips 
As far as inputs i prefer SPDIF and AES/BU
The only thing the new Dacs have are
I2S etc. which I don’t find musical.

My first DAC was a new PS Audio Ultra Link... that was followed by an Ultra Link II which was much better. From there I moved into one box with a high-end Marantz player ($3500) I didn’t care for and sold after about a year. I replaced it with a Sony XA 5400 ES, which was a Stereophile A+ component and extremely good on Redbook and SACD. I’m streaming now with a Cambridge CXN (V2) feeding a Benchmark DAC 3b. I listen to lots of internet radio at 256 and 320 kbps and then go to Tidal and listen to albums when I hear an artist I like. The Benchmark is also Stereophile A+ rated. As far as source material goes the Cambridge and Benchmark are significantly better than the Sony and both are A+ rated. The only thing I would add is that I spend lots of time on wire and if you haven’t spent time with different digital cables (and interconnects) you don’t really know what you system sounds like. I’m presently using the best of 9 digital cables tried so far and have #10 coming to try. Funny thing is #9 is very popular in Japan but not sold here, #10 is a 75 ohm digital cable also not available here

Where I think you will find significant differences are not necessarily confined to tonality, the differences are quite apparent in the sound-stage presentation. Width and depth of the stage ... the definition of performers outline and their location in the performance, not only side to side but front to back and their isolation from each other within the performance, as well as the layering of depth of stage. These are the areas I have noticed huge improvements in with one of today’s top DACs while still using the same amps, speakers and pre-amp as I did 25 years ago.
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I have a Kora Hermes II (tube DAC) that is very analog sounding. It’s gotta be at least 20 years old?  I put a couple of 1963 Bugle Boys in it and love the sound. Some May wince when I say it sounds very analog, but its smooth as silk and clear as mountain spring water. I know-weird analogy?