canadian kido

Ok boys and girls have a question for you on the 2011 Ram 3500 mega cab with the Alpine system. I want to install a high level in my truck but i have no idea what speakers to tap onto. The truck has the Alpine system in it (9 speakers) with no factory sub then again I dont know if they even come with one. If they did i would use thoese leads for my high level input, of course. Would the truck come pre wired for the factory sub if equipit? if so where would that plug/harness be? I have heard multiple things ranging from using the front door speakers to the rear door speakers, I dont have a O-scope to test the frequencies so i'm kinda stuck. Has anyone done any installs like what I am trying to do, if so I would be glad to hear what you/they have done.

Thanks very much