If the JBL system hasn't been an issue, then why reinvent the wheel. I realize the point here is to make money, but replacing drivers, etc. should make you as much money as replacing the boxes and then suffering a bad rap if an act comes through and raises hell, or refuses to work the site, because of your decision. Give this some serious thought, and if it were me I would repair what's in place, or replace those boxes with a JBL equal. I'm sure if explained properly the venue will understand.