Sonic effects of 20+ year old crossover capacitors?

I was watching those brief PS Audio YouTube videos and Paul talked about how the capacitors in speaker capacitors dry out over time and after 20 or more years, he suggested spec’ing the same rating of capacitors and replacing them. 

Now I have Thiel CS 3.6 speakers being driven by Bryston electronics and man they sound good. Could be better though. How I know this is just by how revealing they are of changes in any part of the system. I’m getting some veiled vocals, and muddying of background vocals. I still get some treble glare which I understand is remedied mostly by better (able to drive lower impedences) amplification, which my 4Bsst2 mostly handles. Bad recordings can still be unlistenable at times but I have found that as I have improved things, even the bad recordings are tolerable. 

Anyway, I just sent an email to Coherent Source in Lexington about this exact issue for these exact speakers. 

But I am asking, in general: for speakers older than 20 years old, how much freshening up of the sound can be anticipated by swapping in replacement (upgraded?) capacitors of the same specification? I don’t know how pricy this can get. I don’t even know what my crossover looks like inside of my Thiel or even how many capacitors are on the crossover. So if anyone has done this service and can testify to how the post-service audition sounded, I personally would love to hear about it.