Right, just bare in mind that i'm a real noob when it comes to car audio

My right hand door speaker rattles'fizzes at certain volumes and on certain songs, and was wondering wha

it could be... could it

be a lose connection? or a split in the speaker?
would it be worthwhile upgrading all of the door speakers or whatever? how much difference would it make, considering I wouldn't really want to spend anymore than £100 really... as in would I actually notice any difference?
This is my current headunit which my dad gave me:

What would all you car audio experts reccomend I do, should i just replace the dodgy speaker/fix it or buy a new system

, if so what should i get... baring in mind i know like nothing about car audio stuff...
also can you spray paint the grills of the door speakers without afecting the sound? I can't imagine it doing anything but would rather be sure...
Any help would be great

Cheers, Les
