Ok, a few corrections, the rear subs are 6x8 or 6x9, I think 6x9's and they are DEFINITLY NOT anywhere near 100 watts. they are AT MOST 20 watts each (RMS). For the crossfire factory system, the way it is configured it is best to replace them with the factory speakers from the dealer if you are using the factory radio. The door speakers are 6.5" component speakers, meaning a seperate tweeter and woofer. It is best to replace these with component speakers, not coaxial.

The rear subwoofers are EASY to get to. All you have to do is move the seat foward all the way and lift the carpet cover up and you will see the speaker.