I just got a '04 Cadillac CTS and I would like to add some subs to beef up the lower end. Is it possible to add subs to the stock system and if so how should I go about doing it? My CTS has the Bose Premium sound system with the sub in the rear deck and a built in 6 disc in dash changer. I want to keep the stock system because it has the in dash changer and more importantly I have the Nav system which the radio is tied into and I don't want to lose the NAV system. I was wondering if I could just take the speaker inputs to the sub and just connect them to the high level inputs on an amp for the sub to get a signal that way? I know that that is not as clean as running in RCA's from a seperate pre-amp, but I am hoping that it might get the job done. Any advice would be great.