I have an 04 Cadillac CTS (non Bose) and I want to upgrade. I currently have 2 Kicker 12" Solo Baric L7s in a box and a Kicker Kx3 crossover sitting in my garage I would like to use. I want to get 2 sets of Infinity Kappa 6.5" speakers or the front and back. What else do I need? I heard I need some sort of VW harness and obviously a new deck. What amp(s) would you recommend to power everything? Should I replace the tweeters as well? And what other random parts (cords, caps, terminal things?) would I need to get everything working?