I have the 04compg and with the monsoon satelite radio. Im really wanting to keep the factory headunit. Add ipod interface and keep steering wheel controls. Add an amp and sub and new speakers all around (except for the center speaker). Any part #'s and wiring tips you guys can offer? How do I splice into the existing amp's wiring? Do I need to leave the old amp live so the factory headunit senses and sends a low voltage output?? -then wire into that output? Sure could use some help!