isn't wira door panel complete cover the speaker? erm..
just do something to make ur door panel not rattle...sound prove or wat..
sometime is the clip inside ur doorpanel loose..sometime use double side tape to put btw those moving part..try do it..dun waste money for the custom door panel..it is not used to reduce or eliminate rattle sound..it is used for a best sound stage..dun get fooled....

actually if u proper installed it, it wont create the sound of ur speaker hit the metal..it's just other part of ur door that are rattles....
if ur spk will hit the metal and generate noise, then ur speaker are not secure tightly..