B5 audio set up help

[JAM3S121]

I am somewhat new to this area but I really want to get some good sound in my car. I have a friend who SHOULD be able to do everything (he works on his hondas religiously but we have some issues where he didn't know what was wrong with my german car..)

My current set up is from the previous owner, and its really old.
It has a old clarion head unit, and amp with 4 polk audio speakers.

The amp is 50 watts x 2 channels and it has all 4 speakers connected to it in the rear the car never had a bose system.

I am planning on getting
http://www.sonicelectronix.com/item_37942_600W-Kicker-Crossfire-Complete-Bass-Package.html?from=857
http://www.sonicelectronix.com/item_43586_Kenwood-KDC-352U.html

I have no idea about the size of the speakers though, and I've read some storys about needing brackets to fit speakers in the doors. My car just has front door speakers and rear shelf.

The current size of the fronts is 3.75 inches which seem small, I want bigger ones but I can't really find a bracket thats smaller than 6 1/2 inches which I think is fine, but would there be issues with mounting them in the door in terms of depth of the speaker vs door?



thanks for the help I really appreciate it