Quote Originally Posted by Fatboy501 View Post
Spade speaketh the truth. You could spend the speaker budget on a decent set of front speakers, and leave the rears stock for now. Most car audio people don't run rear fill anyway (I do ). You can upgrade the rears whenever you get around to it.
Proper Rear fill includes:

Bandpassed ~3000hz to 300hz
L minus R
Attenuated
Time delayed by 20ms

If you just play the same stereo channel as the front two speakers then you've created two stages that are competing against each other. That's why "most" car audio enthusiasts choose not to use rear speakers. Rear fill is what I posted above