http://www.e90post.com/forums/showthread.php?t=596539
When you replace the Logic 7 system with a new head unit you have to replace
the logic 7 amp to because it uses a proprietary fiberoptic signal protocol that only
the original head unit can provide.
Also the original head unit should be mounted in parallel its covered in the above link.
its better to buy that unit from caraudio craze for support the price is about the same.