Hi mate yeah got my system upgraded by Pulse Audio in Hadleigh Essex with a 400w amp and set off direct replacement speakers for the front and a JB sub woofer for the Boot on Banana connectors and velcro. All linked to the current Mercedes system sounds amazing
I had the sound system upgraded on my W204 with 4 Morel speakers and an Alpine flat suborder. The head unit was upgraded from Audio20 to COMAND Online NTG4.7 (both are original MB units). And dynamat sound insulation inside the doors.
You can get all the bits from www.comandonline.co.uk, and if you are not into DIY they can also fit everything for you. Alfie and Richard are forum members and the job is first class.