Which combination of components (Streamer, DAC, Preamp, Amp, etc.) are most future-proof?

Sure thing 

@kren006 Thanks for a great reply. That does help sort out the factors a bit more for me, and the percentage breakdown and the issue of "primary" vs. "secondary" system is also quite useful.

There are couple "in the weeds" factors which I need to research further. One is related to the media which may have more sticking power than we initially assume (because we’re swamped by the churn). I see vinyl resurging -- and even read an article on cassette tapes as still (somewhat) viable (more skeptical on that one, given the magnetic adhesion factor). Another is the sticking power for the delivery technology. As I watch standards for USB, or wifi routers, or codecs change, I get flashbacks of the "betamax" vs. "vhs" thing. I just recycled a bunch of "firewire" cords and have numerous old hard drives sitting in my closet. All that stuff seems more outdated than the CDs I own, despite the fact that they’re all about the same age, more or less.

Meanwhile, my AR 48s from 1983 are great. My Adcom separates from 1993 still make music. And I still have a Thorens TD166 from the 1980s, too. Those all are just examples of the point you made. I want to improve on them, but they’re not *forcing* me to with the same necessity that some other elements are.

The last factor is about distinguishing among my own motivations. I'm quite ok with swapping out and improving gear because this is hobby and about learning through experimentation. (I mean, who doesn't like to try new restaurants or new kinds of food?) But there's an aspect to this area which leads to upgrade-itis, and that's part-and-parcel of the consumerist culture that's environmentally quite destructive and not related to music listening, which has to be the main goal. I want to know why I'm doing all this.

@kren good suggestion for avoiding upgrade-itis. Audition, audition, audition.

@david_ten I like this advice: "Go out and listen to a well implemented front end with basic speakers. Then listen to a basic front end with "high end" speakers."

I might try a simpler variation of that: bring speakers I know well to a store and try out different front end equipment with it so a variable is eliminated.

Erik, kren: you've made sense throughout, and directly addressed my question. I hesitate about $2k doorstops. But if the DAC is still good...

Anyone try the Bluesound Node 2i as a streamer? The price point there seems reasonable, especially given the likelihood of eventual obsolescence. It has a DAC built in but streams could bypass, I think to better DACS or integrated amps w/DACS.

Sounds like a great system. My gambit is to avoid looking at at least the DAC as a TV. 

@kren0006 I'm looking at the audiolab 600n. Lack of any display on the front is questionable but maybe not a dealbreaker. (Worth investigating and 1/10th of the price of the Lyngdorf mentioned. I'm sure that's a great piece of gear but it is a huge combination of things and doesn't solve the problem of the streamer being outdated.)

@audio-union I love the idea of swapping in new boards as they're available, as long as the company stays in business and/or supports the unit with new boards. Not sure the Ares products are the way I want to go but…

@soma70 Thanks for the advice; I had moved away from separate toward integrated, though now I’m surfing the web about some separates by PS Audio and the preamp includes the DAC, so maybe I’m back in your direction. I wonder which tube-preamp/DAC/streamer you like?

@jrwaudio — I hear you about "where are my glasses"! I am officially middle-aged, applying low-vision standards to my components! That said, I’ve got to just say it out loud: I like a volume knob, balance knob and even (gasp) a bass and treble knob. But they’re not dealbreakers.

@lalitk — agree about Linux. Regarding your question about short/long haul, I suppose the answer is this: lack of a large listening room to build out a system is causing me to rebuild/revise my present system in a modest way — with smaller speakers. A basement remodel is on the longer horizon, but in the meantime, I purchased good small speakers for my office and am now researching better source, power, etc. If and when I can transition to a larger listening space, I’ll have good source and power, and then may swap out speakers. I'll look harder at room acoustics and other issues (cables, etc.).
   The immediate challenge for me is to go step-wise. I just spent $2500 on new speakers and sub, and so I don’t want to spend a crazy amount on streamers before I figure out what good power might cost and which power matches best with my new speakers (they're getting built). I want to spend what’s proportionate on the other components, given the speakers. (I know this leads to a contentious topic, but personally, I’m comfortable spending about the same on source/DAC as speakers and on amplification as speakers, but not wildly more on any other main element of the system.) For these reasons, I’m not entertaining streamers that cost as much as what good power might.

Budget-wise, I suppose this works out (estimating *as if* they were separates):
$2500 on mains/sub (spent)
~ $1500 preamp (researching now)
~ $1500 amp (researching now)
~ $800 DAC (researching now)
~ ?? Streamer (researching now)

@skypunk I’ll look into Simaudio. Thank you!