I honestly mistook the new SLK for an SL. Very, very sharp looking car.
There's only one car that comes close in comparison and that's
The Boxter S, but as you previously stated, it is more expensive and is also a rag top.
Honestly, I don't think you can go wrong with the SLK, not only will it match your S Class, but It'll be fun for you to take out too. Not to mention if you get her the manual, she might get better at certain things.