You really only need one sub-woofer for the space inside that car, this coming from the guy that used to run 2 800w rms Pioneer Premiers in a box that barely fit in the trunk space. I'm now running the stock Pioneer 7 speaker system, its a lot clearer than what I had in my old LT.
My advice is to get a good 4 way amp for the doors and deck, some quality 2-way door speakers and 3-way rear decks. Then grab a decent amp and sub that wont take up much space like the Pioneer shallow mounts.
Unless of course you want ground shaking bass, then I actually have my old system for sale