I suggest checking here:
http://redd.it/29mzytunfortunately i dont have a 280x for setting up but it really should be the exact same as your previous settings. I am trying to get some configs together so I can make a thorough post but I want to assure I have a lot of different algos and accurate results. Either way that reddit post has the modified cl files and I have had reports of improved hashrates with 280x (and generally fixes issues with x11/x13 not working with 14.6 drivers)
i have already checked your post in reddit, and i am still confused, GGin told me just upgrade my AMD to 14.6, my rig crashed. But in your thread in reddit it should replaced the cl file, so which one is right?
MUCH THANKS!