I'm reading a variety of different reports on the sizes, everything from 5" to 6.5" to 6x9 (rears). I don't have my VX on me at the moment (it's still new to me), so I can't recall the tweeters at all. I remember only the door speakers by the footwell, and the rears. What I can say from experience is that you can usually fit pretty much anything in a door speaker, if it will fit the enclosure. Many have plastic mounting enclosures, so if you use self-tapping screws, you can "make" your own mount holes in them & toss in whatever size (diameter) will fit. On my GTO, this meant replacing 6.25" with 6.5". There's a caveat to this though.

You have to make sure the magnet depth doesn't impede the window. If magnet is too deep, it will block the window from retracting. Alternatively, if the face of the speaker is too high, it won't fit properly under the stock grille. Here's an example of what I did with my GTO. I clipped the webbing out from behind the grille, and that allowed me to place the Pioneer speaker grill BEHIND the OEM grille in the car, kind of a "stealth" install, if you will.



Of course, if you can get some aftermarket grilles, (custom make your own, fiberglass your door card, etc)--then there's virtually no limit to size/depth of what you can mount there.