I Have the Haf X blue edition, i ran into the same problem.
what i did was take the 4 screw out of the side panel fan cowling and turned the cowling 180 degrees and put the screws back in.
as the cowling doesnt cover the entire lenght of the video cards,
i ordered a 80x15mm fan to put in the advanced gpu holder. which will cover the section of the video cards the cowling isnt directly blowing on.
also plan on installing the air duct which fits around the right side of the video cards near the front of the case with its own fan for some added cooling.
P.S with the cowling turned 180 i havent seen any difference in temps.