Hej Mikkel,
You should defenitely be able to improve the quality of your sound system without doing any damage to your interior!
Most major manufacturers offer replacement speakers to fit stock speaker locations.
My personal favourite is Infinity or MB Quart, which both have a very "natural" sound to them.
You should check out my (other) website; I've been in the car hifi business since 1991, selling high-end car audio in Sweden. The address is:
www.audiosystems.nu
I don't export to Denmark, but you get a feeling for the available brands (I only carry the TOP-brands!
)
------------------
1972 911S Targa
************************
http://home1.swipnet.se/~w-15567/Eleven.htm