Install questions

Hi, I'm looking for a little advice/help from some of you more knowledgeable car install guys.

I have a 2004 Chevy Silverado with DB651's in the front doors and (I think) db461s' in the rear doors. I've noticed recently how one of the fronts sounds blown. I removed the door panel and took a look at the speaker and sure enough the rubber surround is cracked. I've had these speakers in there for 8 years or so, so it may be about time they start wearing out. Is this a good assumption, or should I expect more life from them?

I also noticed how the mounting screws are all installed at an angle instead of straight into the door frame. It even looks like the head of at least one of those screws was so large that it would be rubbing against the rubber surround causing it to wear out faster. And I did notice that the tears in the rubber seemed to be at those points. Did I have a bad install? It was done at a now defunct company where I bought the speakers and HU.

I plan on replacing the fronts with another pair of db651's. When I do this should I look for a mounting bracket or something similar to get the screws further from the surround? Maybe even different screws with heads that will not touch the surround?

If you need any more info then please let me know.

Thanks in advance!