Upgrading KEF 104/2 Cross Overs

I have a pair of KEF 104/2 speakers and have loved them since they were launched way back when they were about the same cost as my hole years salary ! I intend to keep them for life and want to research the best possible cross over upgrades and then upgrade them of course, now that I am of reasonable means and my speakers are around 24 years old (single wire not bi wire Raymond Cook versions)I am not putting a budget on this quest although common sense will prevail at the end.

I want to ask those in the community for the best advise, methods, components, circuit diagrams and electronic values in any upgrade with a view to my doing the work myself and or an electronics engineer to match and pre test the finished product.

Please could anyone who is in the know give me direction here as I want to plan and begin this soon, I listen to them through reasonably good source equipment and just in case amplification is a consideration I have a Nu-force P9 Preamp and P9V3SE Mono Block Power Amps we all live very happily together in Vancouver Canada, I would greatly appreciate anyone's comments and results in doing so them selves I have aa couple of ideas so far from other avenues but want to get some solid direction before my committing to the project !!!

Many thanks