Teins does sell their springs and shocks separately.
As for the GAB shocks, I've tried them with my eibach springs before prior to my TEINs now and the GAB shocks are pretty stiff. The turn-in response is good but if you plan to use the GABs for daily driving, even at the softest setting, the GAB will probably crack your back sooner than u think...it's nice on the track however