I want to get some lowering springs for my 04 and ive been looking at a few and some of them have major differences in spring rates. Ive seen some that have 4.1Kg/mm and some that have 10.2Kg/mm. Im assuming this is going to determine how stiff the springs are correct? But what is too stiff? Does anybody know the spring rates on a stock 2004 wrx? What works for you guys? Thanks!