Having recently ordered one of these I will admit to a small degree of bias as I inform those of you in the uncool camp as to why you are of course spectacularly wrong in your assessment
Firstly the estate is definitely the way to go for maximum sleeper effect.
Secondly white is far too obvious - a car like this should be black, dark grey or F1 safety car silver.
Thirdly this car is 159 sized - surely that is not "big barge" territory ? I think you might be confusing it for an S-Class.
So why is it cool ?
It's all about the engine - the 6.2 V8 is a bespoke unit unique to AMG and not based on an existing mainstream MB engine, it's built by hand by a single engineer from start to finish who then signs it. If you visit the AMG factory you can meet the bloke in question
460 bhp easily tuned to 520+ in a family motor !!
In an increasingly digital age this is an unashamedly analogue machine with the performance to worry most super cars, bags more character than the equivalent M or RS cars, plus in sober coloured estate mode room for five people in the ultimate stealth mobile.
And lastly if I need to explain why the noise adds to the coolness then you need new ears