6x9s is a good choice but its better to actually take out the stock deck and build a new one out of wood that way you dont become a butcher also with a new deck you can mount the speaker high cause the magnets usually wont fit a spacer would work nice like an extra piece of wood ontop of the deck to mount too then cover the whole thing with a carpet material so its plush. I built a new deck in my 16v 6.5 inch eclipes are there with an 8 inch sub there it rocks