Newb to car audio...need help from the public.

[lt_370z]

I am looking to upgrade the front speakers and throw in some bass with a 12" subwoofer. Now my question is what would be the best choice for an amp if I want to run this set up?

(speakers)
Amazon.com: JBL GTO638 6.5-Inch 3-Way Speakers (Pair): Car Electronics

(subwoofer)
Amazon.com: Kenwood KFCW3013 / KFCW3013PS / KFCW3013PS 12 Car Subwoofer: Car Electronics

I am clueless when it comes to car audio so I thought I'd get some advice from people who know this stuff better than I do. I've did some research and if I'm not mistaken I need a 4 channel amp to run the speakers and the subwoofer to the amp? I am very hesitant on purchasing a head unit because of the car theft rate around the Houston area lately so I will probably be sticking to this. Any advice or recommendations are welcomed. Keep in mind I'm not trying to spend a whole lot of money on a system. Thank you!