HI
I just did the install on my Oz 06 rav4. The speakers in there are moulded into a plastic mounting bracket which is riveted to the doors, both front and back. The size of the original speakers is really irelevant as you can't reuse the bracket anyway, when you see it, you'll understand why.
I made some 1/2" thick MDF cutouts and installed 4 6.5" pioneer speakers, 2 front and 2 back, and they fitted easily, ie: no cutting of the door panel or trim. The space in the door is huge, I reckon with a bit of panel work you could get a 6"x9" in there.
Plenty of depth so no problems with hitting the window.
I drilled the original front tweeters out of the brackets and reused the bracket. The rears were simply drilled through the door panel.
Speakers I used are here:
Pioneer Australia: Car Entertainment: Audio, GPS, Navigation, Speakers, Subs, Team Pioneer - Pioneer - Car Entertainment
As per the previous post, there is an install post in this forum.