Here is what you need to do. Pick a setup that is for similar conditions as where you race. Get the springs for that setup, and the next softest and next stiffest pair. If you regularly run at a couple different tracks and the conditions are very different (outdoor, bumpy, and loose vs. indoor, smooth, and high bite) you might want to find a couple different setups for those conditions. Basically pick a setup, get the springs. Really not as complex as you are making it. The other option is to just get all the springs and be covered no matter what.