I am no expert in this area but I can tell you that I learned alto at this website. http://forum.sounddomain.com/
I am in the process of getting a system for my car built up and so far I have a Kenwood KDC-MP922 head unit, 1 Kicker S12L7, and a Kicker KX600.1 to power the sub.
Make sure that you get the right subs for the right amp, or vice versa. This is the mistake I made when I bought my sub since it is a dual 2 ohm voice coil, not the dual 4 ohm voice coil model that I wanted. The amp I have will only push 300 watts into the 2 ohm VC, but it will push 600 if the sub was a dual 4 ohm VC model. That's the small stuff that will kill you if you don't know what you are buying. I am going to buy the dual 4 ohm S12L7 if this sub doesn't sound good/loud enough once it's installed. It's also in a sealed box that is around 1 cubic foot since I want to keep the trunk as empty as possible. I like Kicker Solobarics the most since they always sound great if setup correctly.
As far as components go, there are lots of brands out there. If you got the money get some mids and tweeters instead of the coaxials that most people get. I don't know how much you are going to spend but take your time, shop around(shopping.com is a great site for prices), and listen to each speaker(that's the tough part). CDT, DEI(Viper), MB Quart, Infinity, JL Audio, are just some good brands that are out there. Amps are another story and I would get a class D amp if you can.
There's alot more to talk about but I would go to the site I mentioned above and spend some time reading. I learned alot the first hour I was on that site. HTH