where do most people tap into rear door speaker wires for a high/low converter? I do not have stock subwoofer I want to add my own. Wanna use stock radio for now. I would rather not remove door panels. Is it possible to catch the wires at the side pillar were front seatbelts are mounted? If so what color wires should I look for? I know others have done it but searches dont give me the "whole" answer.