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

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)

What dac you have that uses the 1543 chip?
A french dac  with an internal battery,a NOS one, designed by Christophe Mariac, bought on EBAY... Starting point systems dac....

Look for one used anything below 200 bucks will be the right price...
About 10 years ago I purchased a NuForce uDac for my 2011 MacBook Pro. I distinctly remember it sounding much darker (and worse) than the internal dac on the Mac.

Fast forward to about a year ago. I purchased an Emotiva BasX Stereo Dac Pre something or other to try to replace my Oppo-BDP105d + miniDSP + UPA-200 combo. Again, it sounded “dark” compared to what I was used to with my current setup. 

In that case it could have been the optical input or the amp, dunno, but it sounded distinctly worse than the pricier separates. Even my wife chimed in that it sounded inferior and she liked the idea of a net profit from selling audio gear. 

Poorly designed dacs sound poor I guess. 

Why anyone would throw a ton of money at a dac at this point is anyone’s guess. The specs I see on even $200ish dacs are better than my Oppo’s at this point and with multiple outlets testing equipment these days instead of just word vomiting audiophile speak, you can visually see if what you think you hear lines up.

I’m considering picking up one of these $300 Topping or SMSL units to see what the fuss is about with DSD and MQA. Formats are kind of a wildcard I guess since it’s about what they’re converting not the hardware used to convert. It’s inconvenient because Tidal is built into the Oppo and easy to control from an iPad, but I’d like to know if these newish formats actually improve the listening experience.
As an aside, the Oppo has paired perfectly with everything I’ve ever thrown at it from tube pre’s/amps to tube/ss combos and so on. Backbone of my system ever since it was released.
I own a now very old Chord 64. It had (has) a very peculiar system of resampling and elaborating the SPDIF signal coming out from my sturdy CD/SACD sony player used as transport, which is working flawlessly since the start through all this years. Chord had/has a special sonic characteristic, which I still enjoy! Apart from the loss of an USB input that I don't need as I stream my nas stored UHD files I'ma happy with it and I never thought of changing it
My modified Sony SCD-1 SACD is around 20 years old (modded back then) and I still love the sound from it. It can only output analog from it due to the mods.

My 3 other DACs are all brand new models. They sound cleaner but when I hear DSOTM or Santana’s Caravanserai on SACD I am taken to another place.
I listen to an old (late 90's?) Theta ProBasic III DAC and use digital for CD's only. Sounds great to me...
You can see my earlier post for this thread above.

Anyway, I just received on Monday afternoon a new Soekris DAC 1421, which is single ended, from Mod House Audio. Just thought I would try it as I have been thinking about finding a new end game DAC. I have been considering Bricasti, Denafrips, Metrum, Mojo Audio, and Schitt.

Right out of the box I could tell the Soekris was providing more detail but I also thought it was thin sounding and bright. This was while listening to  "Argus" by Wishbone Ash. I left it on overnight. This morning, I still felt it did not sound very good while listening to "Crossing Muddy Waters" by John Hiatt. A couple of other CDs later, I was listening to "Tunnel of Love" by Springstein and it started to sound different. 

Cutting to the chase, I am listening to "The Touch of Your Lips" by Chet Baker right now at after the DAC hs been powered on for about 20 hours. I know the sound of this CD. The Soekris sound has solidified and I would no longer categorize it as thin. It is smooth to the point of being liquid?! The increased detail seems to be translating into more solid images and better clarify the whole audio range.

So...this 899 dollar and 2.2 pound experiment is leading me to believe that current DACs can sound pretty darn good and I am now questioning the sound quality of the Theta. The next question right after that is whether spending bigger bucks for better power supplies, more nuanced analog circuits, etc. will translate into better sound?

Thanks for listening,