The question is do want springs for dropping or springs to handle better??
If you are looking for drop, then Eibach seems to be the happy one, not to stiff and offer a nice drop.
If you want handling, I would look into either the Racing Beat springs or the JDM Mazdaspeed springs. You can find info about the JDM Mazdaspeed springs at the Protege FAQ, and obviously Racing Beat as info on their springs.
Then if you want to go all out, the JIC coil overs are supposed to be really nice.