What is your definition of a long time? 4 years 6 years? Since you plan on keeping the car for a long time then yes you should do it. I haven't kept a car for more than two years. If I was planning on keeping the car for an extended period of time then I would do it. I don't see spending $1000 on a car that I'm getting rid of in a few years. The rustproofing will deaden some of the sound. If your going with a big system then you'll probably need more. Get rid of the extended warranty , I'll take my chances.