Rear Fill?

No Lanzar = the dumpster, personal opinion but one formed by experience. As far as the speakers go, there is no rule about rear fill. I like rear fill. All of the competition SQ vehicles I have done have used a good rear fill speaker. There is absolutely nothing wrong with using a component speaker for rear fill. People use a coax in the rear as it is one of the least important speakers in a system. You also do not go to the movies and listen to the entire movie through only the rear speakers. Thus the front stage, rear fill.

The rear speakers are louder as they are more than likely mounted in a trunk, meaning they have far more airspace behind them as compared to a door. They are also on a more direct path to your ears in most vehicles. In some vehicles, like a GM pickup from the late 80's for example, the stupid speakers are right at ear level, 6" behind your head. Thus they blast you deaf in no time flat, what wingnut dreamed up that idea.... Lots of things can influence how sound works in a vehicle. The gain on the rear amp might be set higher than the front, the crossover may be set lower, the speakers may be more efficient, the rear amp may be larger than the front one, the fader on the deck may be set incorrect, lots of things to consider here.