I have the same sound system in my '99 CLK, and I totally agree with you on all your points. The reception and sound quality are much better in my '75 BMW if you can believe that. The problem with the bass isn't so much the quantity, but the quality... far too bloated with no definition. And I think that the hidden antenna does nothing for the reception. So my point is that I don't think that the problems can be solved by switching the head unit, unless of course your main objective is to get a CD player out of it. But then a good new head unit with a built-in CD player plus installation will cost you about what MB wants for the trunk mounted changer anyway...