With either Spring kit, your standard Shocks are going to be 30 (for Pro Kit) or 40+ (Sportlines) mm more compressed!
So if you have to drive over speed bumps, at any speed, as you drive over, the suspension might bottom out and your Shock will hit the end of its travel. Over time this is how the seals in the shocks perish and start leaking.
So, you either drive over speed bumps VERY slowly, or 6 months down the line upgrade your standard Shocks too when they start leaking!
I'm also in this dilemma, Pro kit or Sportlines, and am more tempted by the Sportlines....
If Im going to lower the car, I want it done properly (not half way). So I've come to accept that having to replace the Shocks too in the (near) future might also become necessary!!