At the end of the day the decision is very personal.
As Mercedes' German lit said on the introduction of the then new baby Benz,
"Der Einstieg in die Mercedes-Klasse hat vier Tueren."
(Entry into the Merc class has for doors.)
It was a swipe at BMW's small 2-door, with its attendant inconvenience.
If you have one or two cars and space and money are factors, in my opinion
it is better to buy a four-door, as the days of two doors to get the price
down are long gone.
I bought a two-door two years ago because I wanted a convertible, and
there's nothing sensible with 4 doors. Luggage space is low but, as we have
only one sprog, we can load up on one rear seat also and can travel for
about a week.
The CLK hard-top has a proper boot/truck, so that's less of an issue.
Getting in and out is nice in a foor-door, but how important this is depends
on how often you carry three or more passengers.
You already have a spacious vehicle (X5) so it doesn't matter that much what
else you get. What is the purpose for that third car? If it's not a
two-seater, why would you want a CLK? A convertible would certainly give
you something of greater difference.
NB: To reply directly replace "nospam" with "schmetterling"