Cutting springs is not a bad idea. However, I would not cut stock springs, they are too soft to begin with. By cutting them, the car will drop but the ride will not be pleasant, likely bottoming out on large disturbances. Ride comfort is determined by the combination of springs and dampers, with the dampers affecting comfort more-so than the springs. I think Eibachs with Tokico Illuminas should give a comfortable yet sporty ride, plus the Illuminas have adjustability so they can be set for cruising or racing. You say you'll be using Tokico dampers, but which ones? From your sig pic, it looks like your Z is already lowered. Are you trying to lower it more?