ive fitted some 6s in my clio and when i removed the door cards there was a hole in the metal waiting for speakers, also had the wiring waiting for speakers, all i had to do was cut a hole in cards so the speakers could show through and would not touch the sides of the cards whilst playing music. i still get some mad rattle but if its loud enough

you cant hear it lol.
i managed to break one or two of the plastic retaining clips and he back side fell into the door housing so thats where my rattle is from :S lol
also some broken glass in there.....

hope it helps,