I have a chance to pick up a set used and was curious if anyone has them on their car and how do you like them? Are they really stiff due to the 10Kg springs? Tough on the street? I'd use them for daily driving and for track/auto-x. Thanks.

 

You'd be fine, 10KG/MM is not very stiff ... Acceptable for road use, just dial-down the damper settings.

 

If you want to drop an inch or so then the Tein suspension is awesome. It has a wide range tunability and not very stiff at the stiffest setting. I will go for Mugen cuz the tunability range is much wider especially the stroke adjustable (adjustable shock length), with that you can lower the car for more camber without scraficing the suspension travel.