[akhter]

I was digging around Japan BMW links, and came across this:
http://www.a-tack.net/

It seems they offer an e90/91 factory fit speaker upgrade option. I can't read japanese, but does anyone have any experience with these? I am going to write to them or get my Japanese friend to call them.

update:after translating with babelfish, it seems its mid/high speakers + crossover, which probably opens up the way for aftermarket amps. They also have links for the window l+r tweeter housing incase you have the low end (non-US) system.

Very interesting...