I dont see why everyone is suggesting all the wrong speakers for his situation. You're recomending speakers that need a great deal of power to make decent sound. Keep in mind, the OEM cd player will only put about 12-15 watts to each speaker, hardly enough to properly power those speakers mentioned.

Your best bet, go to www.crutchfield.com, get the 800 number and give them a call... tell them exactly what you want to do, and they will explain everything in plain english as well as help you select products that will be right for you and fit your vehicle properly. They'll even provide cool wirring adapters so you wont have to cut or splice any wirring in the car, just plug it all in. For best overall sound, replace the front and rear speakers. Crutchfield has a few good specials going, like with Polk speakers, buy one pair and get a second pair at half off. Polk speakers are excelent too!