X99 SLI PLUS - No Picture

Hi,

I've just finished building my new PC.
CPU: 5960X
MOBO: X99 SLI PLUS
RAM: G.Skill 2133 4X8 (A quad channel kit)
VIDEO: 3 X AMD 290
PSU: LEPA G1600

I turn the PC on and there's nothing on screen. Tried connecting the monitor to each of the video car...