Thread: how to setup car system

Hi
I just bought the macvision GPS system which plays mp3s. I want to use this to play MP3s in my car, but dont know what i need to set this up. Its a pontiac sunfire and i dont want to remove or buy a new car deck.
I think what i need is an amp that can connect to my existing speakers and a sufwoofer + it should have rca in, to connect the macvision.
car deck to amp
macvision (rca) to amp --- existing speakers + subwoofer

So that i can use my existing system and when i want to listen to mp3s i can just turn on the macvision and play it.
Is this possible, does anyone know of an amp that can do this.
Thank you for any help