You don't want any midbass only speakers for the rear. Even though the vast majority of your image comes from the front spekers you still want to have full range speakers. Do some nicer components in the front and some nice coax's in the rear. I would highly reccomend taking a listen to Kenwood Excelon speakers. They sound AWESOME for the price you pay <$300 for components and about $150 for coax with high and low pass filters built on. Check 'em out.