^DSP wasn't crap back in the day, but by today's standards definitely falls short.

OP, unfortunately, you will have to do some major work to get your E70 to sound better if you do have the base level sound system. If you are just looking for added bass for mids and lows, adding a 10" aftermarket subwoofer/amplifier will be all you need. Will take up minimal amount of cargo space, but will take up some.

Another user did this, looks clean, and probably sounds pretty clean as well.

https://xoutpost.com/bmw-sav-forums/...install-4.html

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