Yes, the rears are very important. If you are using subs, you can cross the rear deck speakers at a higher frequency so they play mostly mids. If you don't have subs, a very good set of 6x9's are recomended. I use Boston Accoustic, and they are among the best. You can also look at Quartz, Alpine, JBL. I would recomend getting the speakers to match as closely as possible to your fronts. But don't let anyone tell you they aren't important.