I've had the BSW Stage 1 speaker upgrade installed in my 2010 335d with BASE audio (6 speaker w/iDrive) for about two months now. I'm no audiophile, but the BSW speaker upgrades made a significant improvement in sound quality. The kit includes front and rear tweeters, which were not included in the base audio system for '10 E90's, so I'm sure that accounts for some of the improvement by itself. At normal listening volumes across a wide range of muisc types the improved sound quality is very noticable. It's really sad that BMW would sell a $50k+ car with such as lackluster system to begin with, but from my perspective the BSW kit makes the best of it for someone (like me) who wants a relatively simple (more or less) plug and play upgrade. I should also add that I ordered the optional sound deadening material and applied liberally to the door panels during installation. The installation itself was pretty easy, although having to reference multiple sources for the complete installation instructions (web/PDF, YouTube, printed supplements) was not ideal, as it's been awhile since I've done any interior DIY-type work and I didn't want to make any stupid mistakes.