Listening in the car around Norwich and to me, the audio is damn near perfect. Very loud, nice width, punchy but not over compressed. At home, on a quality separates hifi tuner through an expensive set of headphones, it does however sound a bit harsh with some phase type distortion on the high end. I would say leave well alone as most of the 648 audience is likely to be in cars or using smaller portable radios, where the current Optimod set up will always sound best.