@Jeff Matthews, everything changes when you change anything, whatever balance you have now will be different if you take a different path. Whether you like the change or not is entirely your business. Different is fun too, but the engineers had a plan.
It looks to me like you have type A crossovers in there right now. I am going to ASSUME the tweeters are the round magnet Alnico version and the K-55 is the single phase plug version as well.
The type of drivers in your speakers are an important consideration when choosing a path. There are limits both in frequency response and power handling depending on what drivers you choose to use.
If you like the way they sound now, new polyesters will preserve that presentation. Probably make it a little clearer considering the age of those capacitors in there now.
@jjptkd’s idea about trying different caps is a great idea. With a little effort and a very small outlay you can be sure which path you prefer.
I really enjoyed a pair of Crites A/4500 crossovers I had recapped with polyesters in a pair of LSIs (before Crites offered a copper version), albeit with aftermarket tweeters.
When pushed a little harder they held it together better, but at low to moderate levels, the “bright” Sonicaps were more revealing. Your ASSUMED alnico tweeters won’t appreciate being pushed hard, so that is a serious consideration, replacements for them are not falling off trucks.
IF I understand the driver complement in your Khorns correctly, I would expect the type A crossover using a K-55 that rolls off at 4500hz to sound very similar to what I was using.