hole there is for the sub. 8" size. needs to be free to air.
don't bother using 6x9" in the rears, they will muddle ur sound quality. if anything, best bet is to upgrade ur fronts to components and try not to go for the mainstream brands. have a budget for them and then go to caraudio specialist stores to see what's available. My splits were $500rrp, but i bought them for less than $250 since they were last year's models... sif u can see or hear $250 difference... but yeah, shop around. next bet is to install and amp, and if you terribly need bass, add a subwoofer. the small the sub the tigher the sound, larger = louder doof. i started with 2 10" subs, cutting back to one, now i've sold it and looking for a 8" free to air one for the parcel shelf just because i don't want to sacrifice boot space. you will realise that over time, you'll appreciate the basic setup but will produce wonderful sound and that the number of speakers is just a bs marketing fascade... like ppl comparing size of their d**ks with number of speakers in their cars.
its quality, not quantity..
try
www.caraudioaustralia.com - they can help alot there