i personally would run with a decent set of midbass speakers in the rear. you dont want much high freq coming from them that will pull from your front stage. or just use a coax with less power applied then your front stage. you actually dont want to hear them much but if DONE PROPERLY will give you a much warmer sound then haveing nothing at all in the rear. i recommend getting baffles for them too so your subs dont distort them. this is very hard to achieve but once you get it right it is great and you will from then on feel it is of great importance to your system. alot of people have strayed away from this because it is so hard to get right and alot just dont even try and dont understand, possibly because they have been told otherwise. i would at least try it out. im not one to tell someone not to try things to improve the sound of their system.