ok i need some advice from you veterans. i have a 2005 300c that has the boston acoustics 10 speaker surround and the 6disc changer with nav. what i'm trying to find out is, i want to add some kicker 15's and a 1900 watt spl amp. but i'm not sure where to get all the adapters and things to make this work. do i need to replace the head unit and wire a pac connector in, or is the a way where i can keep the factory head unit and just wire them in. i'd greatly appriciate any advice, i've installed pleanty of stereo and subs and amps before but i haven never delt with a car with a factory amp. any suggestions?