That case is not a good one, your putting really nice hardware in a crap case that is not built well and could be problematic for the life of your system, you want a cheap looking case that is built really well and will stand up over time perhaps take a look at the Fractal Design Arc Midi R2 for under $100, it will last through a few upgrades real well and supports 140mm fans all around.
No need to OC your 770's as the ASUS DCII will rock hard for you at stock settings and stay plenty cool. The Hero is a real good MB that will deliver 8x8 on both cards, that is plenty to keep those GPU's fed with data, you would not see 1 FPS better with 16x16 on that Hero, keep in mind the 3rd x16 slot is PCIe 2.0 up to x4 (using the lanes from the x1 slots) and will not steal lanes from your graphics sub-system if you want to plug something into it.
Just my 2-bits, hope it helps....