This speaker crossover. Advise on improvement

Based on the photo at the link attached, I would say that just by swapping out components, you probably will not realize much of a difference if at all. They seem to use fairly decent components. While you could buy "botique" capacitors and try them, in this case, I don't think it will be very noticable, and will cost a ridiculous amount.

One other path you could explore is to have the drivers measured in the cabinet and have a new crossover designed. That, in my opinion, would have more of an effect. At that time, you could hand select components that would go into the newely designed crossover. There are a few companies that come to mind that could do this for you. If you are interested, I can supply that information.

Depending on quality of present caps and resistors, you could hear anything from very little improvement to major improvement. You need to know the quality of what is in there now. I can't tell from the picture what cap that is.

Don't overlook your soldering skills. Less than the factory-quality joints will most certainly negate any benefits of the better components.

If the speaker is biwire friendly, consider an active XO. This will also require biamping, but this is where the real hi-end magic comes from