Music is recorded in stereo (L&R) so alot of people have stated that rear fill isnt needed if you dont have rear passengers. I still have my subs but I took out my 6x9's a couple of weeks ago and I havent heard any difference in sound at all. My door speakers are more than enough.

 

mine are set to 5 on rear and 0 on front. My left are on 8 and right on 0 (other way if ur left hand drive)



Meaning my speakers farest away are getting alittle more power. So i can hear all my speaker in my car. if i look at them /focus

 

I took the rear speakers out a decade or so ago and never missed 'em. I sit in the front.