If you're using a DVD player to watch films etc, then the rears are important for the surround sound. I have an Alpine 5.1 digital surround sound amp which powers the 4 speakers and a center channel speaker and a dedicated amp for the sub. Ok, its not installed yet but i did have it in my Civic type R and wow it sounded awesome. If you are just using the head unit for music then the rears aint important as long as you have the sound stage set up well in the front.