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

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!

Your current system has potential to be much better, without spending $10k.

Weak links are the c1990 Rega P3 combo and your digital setup.

If you want to improve the Rega in the most cost effective way, then look into having the arm rewired, install a new endstub and underhung counterweight, and purchase the P3 upgrade package.  I would also investigate MC cartridges....$1500 will get a great cartridge and SUT.    

You mention that vinyl is not a primary source for you.  In this light, upgrades to your Rega would be best.  If vinyl becomes more important, I would look into a better table and arm.

Vintage MM cartridges are another value oriented improvement.  A new (used) body and replacement stylus will cost less than a brand new cartridge.  A TOTL Empire or ADC can be found for less than $200, another $200 for a stylus assembly (or $3-400 if you commission a custom rebuild) and you have a cartridge that would cost $1k+ if purchased new today.   Many have praised the JICO SAS styli.  Understand that JICO no longer makes this profile, but has announced they will again in the future (when?).

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.

Hardware (preamps, amps and speakers) have not advanced very much over the past 25yrs.  Improvements have been in quality of parts, and in execution.  Passive parts can be upgraded.  Some say older high end equipment may be inherently better because of more robust power supplies, and discrete rather than encapsulated or IC parts.  Careful upgrades of caps, resistors and wiring can deliver a lower noise floor and greater transparency.

You have the foundation for a great system that will last you another 25yrs.  But like a classic automobile, it requires periodic maintenance to perform at its best.

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. :-)

Older DACs may sound better when reproducing 16/44 resolution for reasons outlined above.....better power supplies, discrete vs encapusulated circuitry etc.   But that is where the comparison stops.  Once you get to higher resolution files, then no matter how good the older DAC may be it will not sound as good as a newer DAC playing high res files or disks.   

Have you compared your SF digital gear to anything newer ?   You really can't determine the answer until you do.....

My digital experience is Marantz CD63se, Audio Alchemy DDE, then Meridian 200 2 box Dac, then Phillips SACD 1000 (while it worked), now Pioneer Elite DVi79 for discs and Bluesound Node 2 for files.   I heard improvements with each successive upgrade.  The Meridian did a better job with Redbook than the SACD1000, but I purchased the later for hi res duty.  The Pioneer Elite sounds as good (sometimes better) than the 1000, while the Node 2 does redbook files and everything else as good as I have heard.

Go all the way with the rega: motor, tone arm wire, sapphire sub platter, weight at end of tone arm, new platter in exchange for glass platter, and wind up with the sound of a Sota Sapphire.