Rebuilding XO's are high on my list for best bang for the buck upgrades. Wa mo betta than swapping out cables etc..The AA crossover has a tweeter protection circuit. PWK added it because high-power SS amps were blowing the tweeters. The A crossover doesn't. Years ago, I had the same year model speakers and rebuilt the crossovers and replaced the wiring.
Link to a search of A vs AA xovers. You may want to post/search on the Klipsch forum.
DIY New La Scala Crossover
This is the original crossover in my 33-year old pair of La Scalas. It still makes my speakers sound incredible. I would like to build a new crossover with a modern look, detachable and more natural sounding. Any suggestion for parts is welcomed.community.klipsch.com
I would figure out that sibilance thing first. I dont think it's your XO's unless you see something gooey leaking out of the cracks of the caps.
Prop up some lawn furniture pillows at the first reflection on the side walls. My wife loves it when I do this!