What size speakers will fit my 1999 Canadian C43?

[supermech2001]

Hi..I recently bought a 1999 C43 that is a Canadian model.Today I discovered that the sound system is not the Premium sound system that Bose made for this model car but it has the Standard electronic sound system with the MB speakers which in my opinion sound terrible! My questions are:
Is the head unit the same for the Premium Bose sound system and the Standard system?My exsisting system does have the fiber optic CD changer and Phone capability.I have a MB 6 disc CD changer in the trunk.
What are the speaker sizes for the doors/front and rear decks?
What great sounding speakers will fit in the exact locations with no cutting?
To bring the sound system up to Bose Premium quality what has to be done?
Any suggestions on where to go for a good quality stereo shop in the SF/Bay Area?

Thanks for your time
Phillip
1999 C43