People will always look at the prices of other vehicles at the same spec, and look at prices accordingly, it's just the way it is, if your vehicle is at the top end of the price bracket, only someone who really knows a good car will take it, if you want a quick sale then sell it at a lower price, if you don't then leave it as is and enjoy. If you get a genuine buyer, then good, if not! nothing lost.
That's a lovely looking car.
I never did see the attraction of using Diesel engines in this kind of motor though.... first thing that puts me off when buying.
I would keep it listed for the duration. If it sells, bonus. If it doesn't, keep hold of it and enjoy it for a while longer.
I remember doing a traffic light grand prix against a CLK350 in my Saab Aero 9-5 HOT of the time.
CLK350 pulled away relatively easily and the Saab wasn't slow (250BHP / 350NM) although the Saab isn't notorious for a standing start - more midrange.