Can anyone give me some ideas for improving the factory sound system in my 1998 E320? The rear speakers boom too much and on the front ones the bass actually rattles the door (you can feel it in the arm rest) but you can't hear it!

I also have a few basic questions:
1. What brand is the sound system? Becker? Alpine? (I have the regular radio and a trunk mounted CD player.)
2. What size speakers are used and where are they? (I know that sounds silly but it's not obvious what's behind each grill!)
3. How do I get the grills off without damage to take a look?
4. Whats the best way to access the speakers? (in case I want to change them.)

BTW, as a hobbyist and electrical engineer I am quite expert in regular sound systems but I am somewhat inexperienced in car audio (it seems to have its own rules!) - However, I would like to remedy my lack of knowledge.

All help gratefully received.

Cheers,