The HAF-X has several water tube holes at the rear top of the case that allows you to run tubing to a radiator outside the case. You can also place a radiator on the top of the case outside and have the fans on top pulling the air. Also like I said one of mine is on a shelf underneath the desktop and the tubing is run to it from the rear of the case. There are always solutions some may take longer than other to think them up.
My HAF-X case no longer resembles a stock HAF-X with the modifications that I have done.
You can test out this idea by measuring your radiators and fans. Make a sandwich by putting fans in between the two radiators and then adding fans to either the top or bottom of the sandwich and see if it will fit inside.
As far as the water block for the 760 I don't see one out yet but I think that there will be soon. I looked at the other video card lines and the water blocks went down to the 560 , 660 models so that would man that the 760 will get one also.
This site is the manufacturer that will most likely make one.
http://www.ekwb.com/
Then these two site will most likely carry that block.
http://www.performance-pcs.com/catalog/index.php
http://www.frozencpu.com/