I would concentrate on the front speakers first if you're looking for the boggest difference over stock. The rear speakers will be noticeable when changed, but nearly as much as the fronts. I happen to like infinity kappas, but everyone has their own opinions. Mainly, you get what you pay for. I also prefer pioneer,kenwood, or alpine head units. How much power is you amp and how much are you wanting to spend? Look in the FAQ and search for the removal of the bose enclosures and such if you aren't already familiar with it. I have infinity kappa 6.5 components in font, kappa 4x6 2-ways in back and a pioneer deck. I love the clarity and definition, sub is a 10" infinity kappa perfect