Hi dr.
you may get a lot of different answers on this but I say yes, if your speaker is pretty good to begin with, upgrading parts will usually give significant better performance. With lesser speakers, upgrading parts will most times reveal the crap drivers the manufacturer used or how poorly the crossover was designed. Not good.
In my experience, the hierarchy is this:
1.) Upgrade signal path Caps and Resistors in the Tweeter leg.
2. & 3.) Upgrade shunt caps in the woofer leg and upgrade coils. Care and probably some experimentation needs to be exercised with replacing the coils because the DC Resistance of the coil can effect the box tuning.
4.) All other Resistors
Replacing the wiring is a very good thing too if it's done right or if some really poor and inadequate wiring has been used.
Cheers!
Robert