After I replaced the front door speakers, I did lose sound in the rear speakers from losing that crossover in the Infinity speakers. Consequently, I had to replace all four speakers, the HU, and also install an amp. In retrospect, I do believe my installer was an idiot though, so there may be a way to avoid this. Also, I did manage to keep my tweeters becuase I went to another (much more knowledgeable) installer, who somehow found a way to splice the tweeter wiring from the front door panels. However, just a warning, since I did that, I have blown one of the tweeters because they just dont seem to handle the power from the amp. I credit that to the general crappy build of the "premium" sound system in the 02 KJ though.