I put a set of MB Quarts in the back. They were drop-in replacements, and I reused the stock grill cover. (I don't remember if they were 5x7 or 4x6, but I'm pretty sure they were 4x6.)
I also put some MB Quarts in the doors, but they required a bit of modification to fit properly. I don't recall exactly what I did, but it wasn't difficult, and I didn't have to cut the door or door panel and also reused the stock grill cover. I think the fronts were 5-1/4".
Both sets sound great!
If you want information on what fits without moifications, go to
www.crutchfield.com. Each speaker listed for the car will say whether it will install without modification to the car and also whether the stock grills can be reused.
HTH.