Ford 'B' springs for you. Lowers the ride, yet doesn't punish you to death. It rides kinda like stock. The 'C' is a bit harder, and most prefer it. I like the 'B' myself. Right now I have some Steeda Sport springs, and any of the Steeda springs will beat you to death. Get the 'B' springs.
If you want slammed to the ground, the Sportlines are rough riding, but I like them better than the Intrax springs. I haven't tried out H&R, Roush, or Saleen stuff.