dude you are way better off chucking the factory amp! technology has improved so much since '84! the new stereo has a way better built in amplifier than that junk in your car.

do your self a favor and just get a kit and harness if you havent already so that your stereo fits perfect, not hanging out or nothin, and you dont cut your wires the ghetto way - it'll cost you like ten dollars! and you will save so many headaches.

then replace the interior speakers you probably have 5x7's all the way around but i would have to check to be certain -it would probably cost you 40 dollars a pair
you can e-mail me if you would like to buy these things i can ship them to you