Audio question

7ers,

I currently own a 06 750 and have logic7. I'm big on audio quality and I am very happy with my current stock logic7 system. If any of you had an older 7 with logic7, how does it compare with the 09 and later 7 series sound system? Is the bass better and overall quality better or about the same? Also my current 7 series has 59k miles and I recently got the first out of warranty issue which is related to drive control, you think it's time for me to get rid of it and get a newer 7 series? I take real good care of my car and maintain and drive it with lots of care Only thing I worry about is that someone told me that turbo engines are not long lasting or reliable as normal engine and they sometimes require turbos to be replaced before 100k miles. Your opinions and advice would be appreciated.

Thanks