Swing head unit distortion from speaker

My first week with my Superb is now complete and I'm very happy with the car with the exception of the head unit and speakers. The seller did say the passenger door speaker suffered from distortion so I was aware when buying but it needs fixed. The radio reception is also terrible on MW which is what I normally listen to.

My plan is to fit a new head unit with DAB, preferably OEM. The car has bluetooth with voice control and a shark fin but probably the one without DAB aerial.  The steering wheel controls don't seem to move tracks when connected to bluetooth though. I'm not fussed with Sat Nav just want a decent radio, bluetooth and speakers that work. 

What is the best way to get OEM DAB while maintaining the current bluetooth functions and also what is the most obvious place to start fixing the speaker. Thanks