It all really depends on how much you want to spend....and what kind of sound you are looking for.
Do some searches on Caraudioforum.com and caraudio.com
Check the For sale sections on those forums, and also check ebay, and woofersetc.com there are usually some pretty good deals.
A quick list of good components would be
It really depends on what kind of sound you are looking for, and what suites your music the best. Poke around on those forums and you will find a great deal of information.