Any 91 S-Class has already a sound system with the amps behind the rear seat backrest. Those two digital amps feed your ten speakers. To drive these amps you need line out or speaker outputs in the 2 - 3 Volt range. Our cable kit supports this sound system. I cant tell you anymore on this board or I am violating the rules again. E-mail me at hbecker@beckerautosound.com