Rockford Rem. Bass / Fac. Amp location

I will be installing two Rockford Fosgate 600.1 amps in a 2006 Mercedes SLK55 AMG in about two weeks. The problem i am seeking solution for is whether or not i am able to converge the two remote bass controls so a single could control both. These are the eight pin connectors. I will be using the factory stereo and he wants to have some extra control over the system. I imagine the best place to find a signal for these amps is going to be at the amp, however, i am not familiar with this vehicle at all and was hoping someone could throw some info my way as to where the amp may be and what wire colors i might be looking for. Thanks in advance for your help.

Here is something to chomp on. Make sure the subs are in separate enclosures as the amps will be slightly different. Next how are you interfacing the amps to the factory system? If you choose the right interface, like a Audio Control 6XS or LC6i + bass remote, this will solve numberous problems for you. It will give you a dedicated sub level control to start, a higher preout voltage so as to keep the gains down on the amp and of course allow the customer to expand the system at a later date if they like, say add better front or rear speakers and an amp for example.