What are some good systems that bump good in the car?
6x9 speakers will give your car a good bass but a sub-woofer is the one that will give your car bump. 12-15 inch woofers will give it quite a rattle. Here is how to upgrade the system http://www.wikihow.com/Upgrade-Your-Car%27s-Sound-System.
If money isn't an issue... BOSE!