I have concert radio (stock system for 99) and recently my front speakers the ones next to the door handels have been rattling more and more. They only rattle when I crank up the music, but now its happening in the mid range, and the rattle is getting louder and louder. Is this damaging to the front speakers or something? Also when I turn the bass way down to -6 the rattling stops, so I was wondering if I put cross overs on the door handel speakers?

The sound you described, and the circumstances which make it "rattle" more, are the signs of a blown speaker. Have your dealer fix it under warranty.
-John P.
-225 TT coupe