Is it good to upgrade the crossovers in your speakers?

I have rebuilt crossovers and wiring in two different speakers, and for the improvement made, looking back, I'm not sure that it was really worth it dollar for dollar. I spent the most on capacitors of course. Looking back, I think with what I know now I would change wiring and leave the rest alone unless there was a problem. My current two pair of speakers are both wired with what appears to be lamp cord, and I know that high quality wire with better insulation will give a better sonic result, so that's something I'm planning on doing soon.

Unless the caps are known to be inferior, I’d leave them alone.  You might stumble into what you perceive as an improvement, but you could also cause some damage, or end up  not liking the change as much as the originals.  

Ten years ago I had my vintage (1978) Large Advents and B&W 805 Matrixes (1997 or so) upgraded by John Van Leishout of Van L Speakerworks in Chicago. I pretty much gave him carte blanche within reason to upgrade everything. I know the caps, inductors, and internal wiring were replaced. The sound improvement was substantial in both sets of speakers. I recall that at some point he called me about various cap options for the B&W's ranging from $200 to $1500 per cap. I am pretty sure I told him to go with something in the $200-$300 range and that my "carte blanche" was not really blank. 

My recommendation is that if you are considering this truly for sound and not also for the fun of the exercise, than have a pro do the work. 

For those advising against diy or any crossover upgrades. Did you have negative experience with crossover upgrades? I've been doing diy crossover upgrades for many years, these have never changed the essential character of speaker. I've only experienced improved resolution, more natural timbre with the parts I've chosen. Duelund, Jupiter, Audyn caps, Path, Texas Components TX2575 resistors, Jantzen inductors, Duelund, Furutech internal wiring, never has a single one of these parts not been an improvement over original parts.

There is no magic in most original crossovers, parts often chosen because of cost or space constraints. Crossover upgrades can one of the most cost and/or overall effective upgrades one can make.

@sns et al

I have been considering the replacement of the capacitors in my speakers which are approaching 20 yrs old. I’ve always heard that 20 yrs is the life expectancy of caps, thus my concerns. Beside that is that I believe there is a slight loss of transparency over the years or expectation bias at work?, Even so, I like the overall sound signature I have and want to keep what I have, if for no other reason, the $12-15k replacement cost. I was told that if I replace with the same values, it should be fine

So, the question is it a good thing to do as a maintenance project? Then too, which capacitors? Nichicon made a big improvement to my 20+ yr old preamp. Are they appropriate for a speaker (original Silverline Sonata)?