I'm in the last stages in my build and need to purchase a graphics card. In regards to keeping the hadron air cool, Is it better to use a EVGA gtx 960 ftw with Acx cooling or should I look into purchasing a reference type graphics card that blows air out of the chassis? ..... I'll be using a Gamerstorm Gabriel to cool the Intel i5 4690k cpu with a z97 stinger core 3d motherboard.

Thanks

Def reference for the Hadron case. I will admit that im biased toward the reference cooler anyway but in your situation you really don't want to dump any extra hot air into that case. The ACX would be cooling your whole case internally since it sucks the internal case air into the heatsink and expels it right back into the case. The reference cooler is built very well too so I don't think youll be disappointed.

Did you saw PNY GTX960 reference design?
I think warranty is longer and look cool.
 

 
But I read somewhere EVGA GTX960 SSC is very silent and fan start at 60C, max temps in games is 70C even fan work only 10% speed.
Such cards is absolutely not comparable with some GTX770 ACX or GTX780 ACX, they are much hotter.  
Temp would be even lower but GTX960 SSC is faster than reference design  because higher clock.
I think you should look little more different options, maybe is even possible to find for little more some cheaper used GTX970 with warranty from unsatisfied customers. If I need to choose reference GTX960 or non reference GTX970 in Hadron I would install GTX970 for any cost, that's not GK110 to worry about heat. People here installed GTX780Ti Classified ACX in Hadron.
 
Edit: Now I saw this...EVGA GTX960 4GB
http://www.evga.com/articles/00914/EVGA-GeForce-GTX-960-4GB/
 
GTX960 with 3-4GB is far better option. 
In that card have power for gaming without filters but need video memory.
Even boost clock is 1350MHz.

Yes but we have some new moments here, now 4GB jump in game.
That's exactly what need to GTX960. I will tell you only one example...
Battlefield 4. 2.1-2.2GB video memory.
GTX960 have power without filters to play smooth only need just little more video memory.
Big advantage is 4GB, really.