Advice on CLK 320 CDI Sport

[imuir]

Decided on a CLK 320 CDI Sport, I'm looking for advice on specification, I have decided on the sport model, what are the must have options as I don't want to buy one say without sat nav only to find a few years later that its a must have option when selling or isn't it that important as these cars.

I have about 15k to spend so should have a few to choose from, thanks for advice.