So are you saying ditch the 6x9s, put two components in the parcel shelf (or is components another way of saying 6x9s) , and a sub in it's own box.
Does a sub need to be completely enclosed? or does it have an exposed cone like speakers do? In other words does it need to have a bit which is visible from the car or can it just sit in a box at the bottom of your boot?
Would there be any problems battery/alternator wise or can the cinq deal with it.