as mob17 said, it's important to first figure out what stock system you have. ms-8 is most useful if yo have the factory base stereo. the headunit can connect to the ms-8 & you can power all of your current speakers off the ms-8's 8 channel amplifier. this will improve staging & sound. you can enhance this further by adding components and/or replacing the underseat subs & adding a higher powered amp. technic on this forum sells a complete wiring kit that would make the install plug & play. let me know if you have further questions. thanks for your interest!
2010 335xi M Sport Blk Sapphire Metallic
2013 535xi M Sport Alpine Wht