I use 350's on mine up front. It's pretty stiff, but I don't drive my car very much and if I do drive it, I don't drive it very far. I guess the good thing about C/O's is that you can swap the springs out in about 10 minutes if you had to. Jack the car up, remove the strut bolt and you are set. C/O's are definately the way to go.
Tim
Tim