Hi,
I don't actually have access to this board but, checking the layout which seems to be pretty standard, I believe you should be able to fit the Scythe Mugen OK.
I have the GA790XTA-UD4 mobo and I have been able to install the Noctua NH-D14. Only thing I had to do was remove the additional heat spread from my Corsair memory as one of the fans sits over the memory slots.
Hope this helps
ATB