Hi Dave,
Wow - interesting ride you have there. First, 17 x 8.0 ET28 is not the correct wheel for your car. You want ET38, which is what I have on my car (17x8 ET38). Also, with an 8.0-inch wheel, a 215 tire is too narrow. I have 225/45 and the wheel is wider than the tire sidewall. I wish I had gone with 235/45 like the tuner recommended (my bad). The ET28 wheels you have will stick the tire WAY out there and rub the fender. You could always install 500E fenders, which would cure the problem. Any offset more than 38 (i.e. ET40) will probably result in the wheel or tire rubbing the strut tube. ET36-38 should work fine up to 235/45 on an 8.0 wheel. Now if you go with a different wheel width, all of the above is out the window and you get to start again.
One other tip: Mercedes recommends a strut travel limiter be installed when mounting wide wheels. It limits how far the front suspension will compress. Your dealer should be able to dig up the info & part numbers, I have them somewhere (need to find them so I can install on my car too!
About the spring issue, sorry I don't have much to offer there... I'd try the regular Eibach or H&R's and see how they sit. Maybe even the OE Sportline springs.
Best regards,