I used 6x8 Alpines and stuffed the cavity behind the grill panels with poly fill. You won't get great sound out of that location no matter what becuase it's not sealed up well enough or rigid enough anyway. Run a crossover and send everything under 100hz to a sealed sub with a seperate amp - like a 10" or 12" in the hatch. Kinda my opinion, but I like the punchy tight sealed sound better. Of course 2 drivers would be louder as will a larger amp. Whatever you prefer. Also don't bother putting the 6x9's in those stupid little sealed boxes you may have seen. Most all 6x9's are designed for free air applications ( trunks ), not little boxes like those and they'll sound like crap.