The US 280CE is strangled with emissions crap, and as such, makes low power and sucks gas. A euro spec CE, even with auto trans, is much faster and efficient. The pre-emissions US spec fuel injected sixes are great, but of course pre-date the 123 coupe.
Otherwise, as others have said, the CD with 617 turbodiesel is the way to go. I have a sedan and a wagon each with this engine, the coupe would be no less enjoyable. Love that pillarless hardtop look.

-JAS