Any crossover upgrade attempt has to be done with willingness to backtrack if your expensive substitution does not work. There is no such thing as a universally better component—if something changes the sound, thst change can be for the better or worse. The switch to air core inductors usually are an improvement. Iron cores are usually used because they are compact and low cost.
Different caps are tricky because people vary in their preference much more and caps take a long time to break in and stabilize; I’ve changed my mind sometimes weeks after an initial impression. I observed a custom speaker being tuned to a customer’s preference. The builder started with some very expensive paper in oil caps, but switched to “cheaper” film caps based on the buyer’s preference; the cheaper caps cost $400 each.
Crossover and Wiring Upgrade
Has anyone upgraded their Sonus Faber crossover, internal wiring, and binding post? I'm a cable and amplifier believer as not all cables and amps sound the same. Using that same mindset, I believe that upgrading the crossover and internal wiring would also yield positive results and keep in my speakers longer versus upgrading.