I do use both. The case I have is one I have sworn by since I had the S3. It's an Urban Armor Gear (any style). Provides a solid amount of protection, I've even dropped my phone (S4) down concrete stairs without any damage. As for screen protector, it's really a personal choice. I wanted the sides covered so I went with ArmourSuit's Military Shield. But, I haven't had it long enough to say. With any screen protector/case combo, make sure the screen protector is cut enough to not be lifted by the case, or you wait long enough for the protector to seal on the screen properly before re-applying your case.