install help..decisions....decisions

I have a 2000 VX Holden commodore...plenty of room to work with..just a basic install...or is it...everywhere i go each individual tells me a different method for my speaker set up...followed by how i should position my subs.
the front have room for a pair of splits...the back speakers have room at the back shelf for a pair of 6X9's tho the factory speakers are in the back doors (6in)

theory 1)
normal install of front splits, pair of 6 inch in the doors then to allow airflow from the boot into the car by cutting out the hole of where the 6X9's are meant to go to allow a naturalport as the subs are in a sealed enclosure (2X 12in 800W polk Momo's.  The bloke who suggested me this also sugested instead of 6inch speakers int he doors, instead to put in another pair of splits in the back.

i was also told 6X9's ar eineffective if the car has a subwoofer and that ime better off goin with 6inchs.

apart from my speaker dilema...there is also the positioning of the subs. If you are unaware of the VX boot setup there is a huge arm rest in the back seat that comes down exposing quite  a gap into the boot...therefore i do not think it appropriate to cut out the space of the 6X9's for airflow as this is more than enough...but which way do i point the subs...facing the back seat and the exposed gap so it hits the back seat and flows right into the car? or the opposite direction like most people do, i want it to sound good both inside and outside of the car  

commodore, not a pontiac, u must be aussie,lol...me too...my advice is, face the sub towards the number plate and close to the rear to promote bass loading, the bass will find its way into the cab regardless so dont touch the shelf, id say some qaulity splits up front and some splits or 2 ways of the same brand and series in the rear...the rear shelf is structural so dont ever cut it or youll be sorry if you get a defect for it, not cheap to fix and not easy to get passed by the rta...  

face the subs to the rear and close to the back to promote loading of the bass, also just use some splits up front and some 2 way 6 inches in the back from the same manufacturer and series as the splits for good sound..dont touch the rear shelf as this is a structural point of your car, illegal.. bass will find its way into your car anyway so dont concern your self with that, any thing else let me know, cheers....are you aussie...