you can use all 5x7's or all 6x8's.
You can use 6x9's but only if you modify the inside of your door...If you do, do this, make sure that the speaker excursion does not hit against any part of the door, or you will hurt the cone of the speaker and your system will sound like a$$.
Jason
00 Audi S4, 2.7 Bi-turbo quattro
01 S10 Xtreme, 4.3l
98' Contour SE with some mods
96 Cavalier (beater)
