As JSP said - there should be an amp behind the LH back panel - if you have the standard mid display - and a centre speaker in the dash. The base model didn't run an amp - or the centre speaker, and the system with the sat nav has a different amp in the back. All the speakers run back to here. There is no reason you can't put an aftermarket head unit/speakers/amp if you don't mind running some more wires between the head unit and the back amp. You can then do whatever you like. Intergration to the steering controls can be done - but I'm not sure of the exact science of this at the moment - maybe one day I will have a play, but the standard system isn't too bad, so it is low on my list.

