[CivicRacerX]

With a lot of civics (I don't know if this applies to the car you're talking about, specifically) I've heard complaints that replacing the rear deck speakers actually entails removing the entire rear interior, including the seats. I assume your CX is not a DX typo, and thus you have a hatchback. If you have interior pods that need pulled out before the speakers will go in, the Best Buy installers might be reluctant to pull at them, for whatever reason. Also, since your car didn't come with them from the factory, the wiring may not be in place. You could try removing the pods yourself and seeing if the wiring exists. If it does, just tell the installers that you had speakers in there before, but they cracked or something. They might be giving a knee-jerk response based on the non-hatch models installation process.

Hope that helps a little bit, and good luck!