A GDB already equip with Sti damper and spring.
Sti red damper with original Sti spring is annoying when driving over street joints. Some have replaced original Sti black spring with those after market pink Sti and said that it's much better.
Tein SS is ok for the money, especially with EDFC - instant adjustable. However, at really high speed it's not so
. It's also a short stroke, you won't be able to jump bridge ramp without spilling your gut anymore. Not to mention a ball joint design, which will make some noise later on and need to be tighten every now and then. Ball joint will wear out faster than those original rubber mount.
Make sure you have all the right information before making a purchase.