Yeah, I can get pretty good performance with lower-spec tech (over clocked i5, 770 4GB, 16GB Ram) and higher settings so surprised you're having a difficult time. Actually your SkyMaxx settings already look pretty low (no cloud shadows, no godrays, really low cloud detail). Lots of users have reported stuttering and FPS issues with newer drivers. Have you tried rolling back to 337.88 which seems to be the last generally stable one?