"Vintage" high end gear vs new and upgrade path?

Thanks to all of you for your comments.  Seems like you're all kind of confirming my own feelings, or at least that we're all more or less of the same mind.  It's worth elaborating a little.....

I don't actually listen to the analog all that much and I'm no longer in the business of collecting vinyl.  I kind of view the Rega setup as "the capability to be able to play vinyl" rather than as a core listening mode.  Now, perhaps that's because the P3/Exact 2 combo just doesn't quite deliver (it's hard for me to swallow that the Threshold pre-preamp is a weak link).  In that case maybe I'm not really excited about vinyl because I haven't heard it right.  So, that said, I guess there's only one way to find out. :-)  Thanks for pointing out a pathway.

Digital, on the other hand, is 99% of my listening and another story altogether.  I can't say that I'm dissatisfied with it in any way.  The biggest variable, by far, is the quality of the source material.  When it's good the listening experience is jaw dropping.  It's fun to sit down MP3-listening youngsters and say "Just listen to this!"   They invariably react like they'd been seeing in black and white their whole lives and just acquired color vision.  It's a magic ear candy. 

Anyway, the digital upgrade path is still murky. The SFD-2 MK3 + D2D-1 combo was regarded as spectacular in it's day, but that day was long ago.  It's also pretty esoteric equipment - not many were made in the first place and they haven't actually been heard by many people.  Good luck finding a review for the SFD-2 MK3.  Comparisons with current or "better" gear are impossible to come by.   Comparing to older stuff, Mark Levinson No. 36 for example, isn't very helpful either (and I'd think that a No. 36 owner would be in much the same boat that I'm in.).  

Other challenges:  I'm gradually transitioning to my music server as the primary source.  The current system can handle 24b/96khz PCM, which is fine for my old ears.  But before shelling out  a lot of $$ I'd like to find some way to make educated guesses on what to look for.  Listening to gear in other systems is pointless IMO and I'm not really in a position to audition equipment - no local high end shops or audiophile community. 

Thanks again and keep the ideas coming!

Thanks to everybody for the input.  My sense from all of it is that there's a lot to be gained by upgrading the TT/arm/cartridge.  That's certainly not a shock. 

That said, I'm less convinced about the digital chain.  Certainly there have been enormous improvements in digital audio, but I'm not entirely sure how that translates into sonic improvements, especially towards the high end. 
But that's kind of a self thread high jack, so I'll take it up elsewhere.  In the meantime  I think I'll fiddle around, maybe tinker at the margins and follow minorl's advice:

But, if it were me, I would listen to what I have and enjoy. When I hear something that isn't satisfying, causes listener's fatigue, lack of space, etc. I would slowly go down the one item at a time upgrade path until I am at a point where I am happy.

>>>snip<<<

In the case of audio equipment, there is always something out there that is better. However, to get to that point may cost a ridiculous amount and (depending on the person) may not be worth it.

Listen and enjoy and go one step at a time.

Thanks again to all!

OK, sound advice, which all helps paint a picture, with one exception:

Digital has improved substantially.   A better DAC will make a very audible improvement.  In fact, over the past few years,  price to quality ratio has moved more quickly in digital than in any other area of high end.  Advancements in electronics certainly help, but also the success of the headphone industry.  Economies of scale in this area have enabled companies to offer outstanding DACs at great value prices.

I've heard similar "digital has improved" comments like this again and again and again. Others say the same thing in this thread.  That's what got me concerned about the whole question in the first place.  However, after more digging I'm now quite convinced that it just ain't so, or at least not when stated so broadly.  See thread below.
https://forum.audiogon.com/discussions/high-end-vintage-vs-contemporary-dac-s-are-sonic-improvements...

I've now come to recognize a related issue:  when it comes to "vintage vs today" questions few people have actually heard the "vintage" equipment in question, so we get general assessments that necessarily don't apply to the specifics.  This seems particularly true in the case of things digital.

My own happy conclusion, more than ever, is that the super high end gear from the 90's (more or less) represents a kind of golden age of 2-channel audio. :-)