Buddy of mine installs systems and told me the stock tweeters in my E90 with Premium sound were worthless! Changed the tweeters to Infinitys, added an amp and a custom enclosed sub in the trunk. I'm 36.. def not into cheesy trunk rattling systems... but it made an amazing difference in the stock Prem. Sound system for all types of music.
Total cost was around $1200..
E90 M3 | Jerez Black | Black Novillo | Carbon | All options but sun shades
Mods: Gintani CB | Dinan Intake | Evo Pulley | HRE P40's | Eibach Springs | MS spacers | Matte grills | GP Thunder 7500 | Venture Clear bra