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 0440/LCGE, 6MT, Sport, Nav, HUD, NiVi (w pin swap in CIC), L7, HD Radio (now from CIC), SiriusXM. Coding: lawyer screen (CIC), Halogen DRLs on with high beams (LMA), fan speed LED seen on "auto" (with an LCI-IHKA), turn signals in HUD (CIC), personalized car ID for BT etc... Complete: CIC retrofit>E90.SSD >E90-E60 merged CIC.trc >coded for Combox and 6NR/6NF.