In model year 2010 in the US they slipped in the lowest grade system they make world wide.
It has no Amp and no Tweeters . If you look in that document in the above thread I posted
you will find it described as the stereo system . There are three systems that were released world wide. But until the 2010 early 2011 build the base or stereo system never slipped into the US market. That document from 2008 is the best description I have found for the three systems.
Many in the US felt shortchanged by this system so BMW changed back to the premium or Hi Fi system after/in september of 2010.
I believe its called the 2011.5 build
Just changing the speakers in that system will not help is it suffers from lack of power
a head unit eq curve that is set up to compensate for a lack of tweeters.
It requires a processor to flatten the output of the head unit , and amp and speakers to improve it.
The following board is the place to go for BMW stereo Mods to the E9x