Go here and enter the last 7 digits of your chassis number: http://www.bmwarchive.org/vin/bmw-vin-decoder.html
This will list all the details of your car including fitted options. Look if you have 676A (business speakers, 11 speakers with 245W amp) or 677A (professional speakers 14 speakers with 650W amp) fitted. If neither is listed you have the basic 6 speaker system.
You can also look behind the seats. If you have a big speaker grill right behind each seat (can't be missed, it's big and behind the nets behind the seat!) then you either have the 11 or 14 speaker system. If you don't have the grills, then you have the basic system. Tweater fittings, etc, are misleading as all cars have them. Only VIN and big grills are telling.
I waited for a car with upgraded speakers and finally found one with the 677A professional system. Mine is paired with the professional HiFi which (when combined with the 677A) also has a Dolby surround option and a 7 or 8 channel graphic equalizer.
Having listened to various system I found that the basic package is crap. The business one is much better although not excellent. The professional one is similar to business in terms of quality but much louder which is nice with the roof down. Unfortunately, even the professional speakers come nowhere close in quality to the top HiFis you may find in a 3 or 5 series. The Haram Kardon system in the 3, for example, is from another world. The one in the E89 does not come anywhere close.
That said, it does sound much better when properly set up. For me personally, it is still lacking bass and mids with way to much highs. Overall the sound does not sound full or balanced. Playing around with the settings helps but I am yet to find the perfect set-up (I may actually start a new post on this

)
I used to have the mid-range speaker system in my E85 (i.e. the non-DSP one) and found it to be on par with the professional one in the E89