At first I was leaning towards a HAF series case however with 2 new recent cases found just not sure anymore. The two new cases/mods I have found are a Antec Lanboy air (only bad thing I've heard is it's size) and the Corsair 600T Special Edition white series. Now the 600T has an interesting mod shown here: http://forum.corsair.com/v3/showthread.php?t=99374
Now I'm not sure which one is the ultimate airflow system, I willbe putting a XFX black edition 7970 GPU in it with a P8Z68-v Pro Gen3 mobo.
haf x = ugly ! so many better choices out there . Truth is sandybridge isnt exactly a furnace and ivybridge is less which leaves ya with the gpu as the principal heat source so if ya got 120mm x 2 or better on the intake and the equivelent on the back your probibly good . That being said buy what apeals to you ! good luck & have fun !
I would also like to point out in the link I posted above the 600T mod gives 12 fans total with everything in. Some slim fans but still 12 total in a mid tower isn't bad. How many Mac can u mod in the HAF x or storm trooper?