well if you want a decent system, i would definately start out by buying a new head unit (the thing that goes in your dash).... here this website is beautiful (although kind of pricey) www.crutchfield.com tweeters are small speakers that deliver very high frequencies, they sound nice, but i dont really thingk they're necessary. If you have money, i suggest getting a nice headunit, replace the stock speakers...that by itself will make a world of difference. if you wanted it to sound real good, get a nice 4 channel amp to run to the speakers, and maybe a sub with a 4-600 watt amp to it....oh and when ya look at the specs for speakers and amps, dont ever go by the peak power...always gop by the RMS rating...that is a mroe realistic number for power output... damn im high this probly makes no sense but ah well, hope itr helps