I keep hearing about how hard it is to get an aftermarket HU in these cars. I bought a new Kenwood EXcelon HU and the VW harness. Installed all that and noticed that the fiber optic and one harness from the vehicle (brown, blue and another color wire) and thought that was normal. Anyway, no sound after the install. Everything lights up as it should. So I need help from you savvy audio/benz guys. I've been told I have to replace all the speakers. Not really trying to do that. HELP!!!