Im stuck on a budget, but these two 6.5 inch speakers look nice, and are very reasonable. I need two sets; two for the front doors, and two for the rear. It's between these audiobahns, and kickers.
focus on your front stage, and don't worry too much about the rear speakers... http://glasswolf.net/papers/rearfill.html
if you really want rear speakers, use a low pass filter to block the high frequencies. Tweeters in the back will wreck your sound stage. http://www.the12volt.com/caraudio/cross.asp
in general, stay away from audiobahn stuff. kicker is ok.