Haf X is full tower case, so why would you think it would have any fitting issues?
There won't be any problem with your case and gpu and perfectly align inside our case.
According to Cooler Master Haf X:
VGA card length: 342mm / 13.5 inch
CPU cooler height: 190mm / 7.5 inch
and according to Asus Gtx 680 top's dimensions:
11.8 " x 5.1 " x 2.3 " Inch
so length and height will be no problem at all to Haf X.
Hey brarboy thanks for the reassurance, it's much appreciated, cheers!!!