What should i add to my car first, a really nice sound system or some engine parts to make it go faster?

If i went with the sound system a would go with 2 12" subs. and of course an amp or two. then probably JL, DD, or IDmax's for the brand. And then i would go with some Focal side speakers(nice ones). And then to top it off a sick deck. probably alpine or kenwood. OR...... i could go with the engine parts. I would go with DC Sports Race Headers, Apex GT Spec Cat-Back Exhaust, and AEM Cold air Intake. I really want to do all of it but i dont have that much money.. I really cant decide wheather to make it sound nice or go fast first! Please leave any help!!!