Go Kart Champion
I'm still on the stock struts, which at nearly 150k are pretty tired. The springs were free, a concession from a dealer when I caught one of their techs abusing my car. I don't think they have a higher spring rate than the stock springs, as I've bottomed out my suspension and bent rims a few times.
I would recommend going with a coilover kit, honestly. You can find a decent set of KW coilovers for around $500, which should firm up the ride some without being jarring.