A Sportsline is a desirable car.
Just replace the struts with OEM Sach's or Bilsteins. Anything else will compromise the ride.

Unless you have a lot of miles on the car then the springs should not have an issue. You wont buy a better quality spring than the ones already on the car. You can have the existing springs retensioned by a suspension specialist - if there is an issue.

The Sportsline featured a lower suspension than the standard models. So. Don't expect the replacements to be as cheap as the stock units. Don't put stock height struts on your Sportsline
Benz carefully matched the struts and springs to special models such as the Sportslines.