don't need 6x9, they are in the trunk and unless you have your seets down, they are useless, take them out put some high end speakers in the front, and something shitty in the back as fillers. spend money on high end amp (s) for your fronts and a sub. Run the back of your deck. Your system will pound crystal clear. The key here is your fronts and the amp powering them... make sure you run lotsa power to you speakers, more then they are rated for...
Once you hear the difference you will realize how shitty the factory HK system realy is...
2001 330ci - Winter beater - RIP
2001 330i - Winter beater - RIP
2006 325i -
2012 x5 m sport -