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), DIRAC 752 Individual Audio retrofit (amp, speakers, coding), HD Radio (from CIC), CDC, SiriusXM. Coding: delete lawyer screen (CIC), fan speed LED seen on "auto" (with an LCI-IHKA), turn signals in HUD (CIC), personalized car ID for BT etc... Complete: CIC.C1A retrofit>E90.SSD >E90-E60 merged CIC.trc >CMEDIAR.C05 coded Combox, w/ ConnectedDrive, Plug-In, etc.