I've got some very fine 1980s vintage equipment I love and don't want to replace.
Well, that's it then, isn't it?
On the principle "don't fix it if it ain't broke," I'm inclined to leave
well enough alone. I don't notice any audible deficit. But perhaps the
system could sound even better?
Right. Changes that are slow and gradual, hardly anyone notices. The frog boils slowly story is there for a reason. Of course the system could sound even better. This is always true! Even right now, me with brand new Tekton Moabs, everyone telling me how much better they will be if only I am smart and replace the "cheap" caps and inductors. They're Mundorf, not cheap, but there are even better more expensive out there and so compared to those yes mine are cheap. Sigh.
Its ALWAYS this way and so the smart thing it seems to me is instead of asking "is it worth it" which no one can answer the better one is, "what can I afford to spend on an upgrade if I KNOW it will be worth it?" Because it will.
The difference is this way you take your budget, look at your parts, and divvy it up. Kind of like building a system. If you know you need 5 things and you only have $5k then you know it can't be more than $1k per thing.
In fact its very similar because if you dig into it some caps the quality is more significant than others. Also its not just caps. Some nice fast hexfred diodes are relatively inexpensive yet make a huge difference.
One really nice thing about this is its not something you even have to farm out and pay someone to do. Cap values are printed right on the cap. Shop around, find a better one, unsolder old, solder in new, done. Listen. If you don't hear it stop right there, probably never will. Odds are you are impressed just one cap can make so much difference. Keep going. Biggest problem usually is to find the room. Better caps almost always are physically a lot bigger, even though the exact same value they are huge, and there simply may not be room enough to do them all.
You won't have this problem in the crossovers. Those are very simple circuits. Just sometimes hard to get at. But if you can - no high voltages, plenty of room, only a few parts - perfect place to start.
My first mod was cap and diode upgrades in a Aronov tube integrated amp. Huge improvement. Will be for you too. Look at it that way. Plan your work. Work your plan.