***Ksport*** What about theese coilovers? Cheap?

[NoHachi]

Coilovers give you hight adjustability...nothing more. You can go shortstroke with ordinary springs too..same rules apply, but its difficult to get a correct ride height and the welding becomes more difficult.
E.g. If the springs you buy have a stiffness and ride height that you like, then its just a question of shortening the strut ABOVE the perch. To be correct you should remove about as much as the car was lowered. Then find a shock that matches the remaining length of the strut..usually a shortstroke shock with maybe a spacer underneath it to make sure it sits snugly in the casing.
Where there used to be a strut casing, there now is valuable bump travel, ready to soak up anything that the road will throw at you.

Forget about ride height VS roll centre etc..Because there is a lot that influences it..rideheight, strut inclination etc. It also moves around as your suspension cycles through its range..difficult stuff.
What you want to ensure is that you keep of the bumpstops and that you retain decent roll geometry (aka negative camber from bump). If you ensure these two things, your suspension will outperform most here on the forums.