The stock B&O system is really bad in this car. Well, all stock sound system are bad to be fair.
So, I had to start somewhere. The easiest seemed to be an upgrade to the (sub)bass.
Prefab box tuned to ~39Hz for 2x8"
Sundown Audio E-8 V5 D4 8" 300W RMS Dual 4-Ohm EV5 Series Subwoofer"]2x...