Do the bass level listening test - settings in your audio menus. What result?
It would be very hard to convert to the DSP factory amp. Truly better to sell and buy a car w that option. Of course, there are aftermarket choices such as an MS-8 by Harmon but that would require some solid audio electronics skills to install.
2007 650i Stratus Gray Black/Beige, 6MT trans, ZSP Sport Pkg, ZCW Cold Weather Pkg, 609 Navigation, 610 HUD, 611 Night Vision, 322 Comfort Access, 677 Logic 7, 653 HD Radio, 655 Satellite Radio.