I just picked up a 2008 M5 with the upgraded Dirac system. It sounds great, but it lacks the thump I need when I'm listening to techno/hip-hop.

I've read that the trunk is sealed like a tank, and the only aftermarket speakers that fit in the under-seats are the SWS-8. So what's the best way to go here? I'm not looking for something crazy that will rattle my car apart - just something to fill out the low end and provide some bump.

Is there anyone that knows how to deal with these fancy e60 systems in San Diego?