either you edited your post, or i didnt read it thru like usual....
if the tweeter door circle trim things are cracking, then you are out of luck... i mean you can replace the speakers, but the trim isnt really replacable... unless if you bought it from bmw, but you have to buy the speakers to go with them... which is ridiculous... you can always look for cars that are being parted
i love my system, its great.
i have infinity speakers all around, all bypassing the oem amp and running off of my alpine head unit. head unit has aux input that connects to my ipod.
i have a custom made sub box from el presidente(i dont think he is around any of the forums anymore... he was one of the most helpful audio guys for me, and that is what he did for a living. it houses my infiniy ref 1230 12 inch sub and blapunkt amp.
with a quick adjust to the head unit eq for different music, it sounds amazing.
some dynomat would be awesome, but too pricey for me.
the funny thing is, when i had all stock audio in my car... i thought my moms BOSE sound system sounded good in her audi... now it sounds like complete shit to me... hahaha