i've got custom spring rate ground control and koni's. great combination, but if you wanna go low and have stiff spring, you need to look into shortening and revalving the shocks for your spring rates.

Once I get my Koni's shortened and revalved for my spring rates, I couldn't think of anything more I'd want from my setup.

Truchoice also makes coilover kits using the Koni, GC method with custom spring rates and revalving already done. More money depending on what level you choose to go with.