Are you running the EPS cable from the power supply in the bottom of the case, over top the video card, then to the top of the board? You might not need an extension if you can route the cable through a hole by the power supply behind the motherboard, then through the cut out that Feronix pointed out. It will look much better too.
I know with my last case the cable was too short unless I routed the cable under the tray. (which should be done anyway!)