Z87-G45 Gaming + Asus R9 280X problem

Hi,

I have the following hardware:

Main Board: Z87-G45 Gaming SKT 1150
Bios Version: 1.6
Video Card: Asus Radeon R9 280X DIRECTCU II TOP 3Gb GDDR5
PSU: Corsair CX-750W V2
CPU: Intel 1150 Copre i5 4670K 3.40GHz 6Mb
Memory: Corsair PC3-15000 1866MHz Veng...