sixto,
The sport package in the W124 and W201 does not delete the rear middle seating possition.
The W202 C36 AMG was available with the regular rear seat (5 seater) and the 4 seater back seat was an additional option. I don't know how the C43's rear seat was set, but I think they came as 4- and 5-seater as well.
The picture below is taken from my car that has a 1996 C36AMG interior.
greetingz,