You don't Need a new case, but don't you WANT one?
I am sure that you can find a good case with E-ATX support, cooling improvements, reduced noise, etc, for not too much money. I'm biased, but the Switch 810 holds my Rampage 4 Extreme with room to spare (it really doesn't even look like it's an E-ATX board when mounted in there), and the case itself can be had for not very much (around a hundred USD if you are a savvy shopper). It is an absolutely awesome case to work in, and the cooling options are staggering. You can fit up to 1x 420 + 1x 280 + 1x 140 rads with absolutely minimal modification, or for air coolers there are mounts for 9-10 fans, and all mounting points support either 120 or 140 fans. The interior "swivel mount" fans attached to the HDD cages are extremely beneficial, as they essentially act as the "pull" fans to the front panel's "push" fans, and the result is that the air is actually able to get through the HDD cages quickly and efficiently, not losing any velocity thanks to the interior fans. The fact that you can aim them is even better, although you do lose a bit of the push-pull thing once you swivel them. It doesn't matter too much because you have the bottom intake, or two if you remove the bottom HDD cage. Both HDD cages are removable, separately (so you can remove the top and keep the bottom and vice versa), which is quite nice if youddon't have anything in the cage as removing the bay gives you a completely unobstructed intake fan. Oh, and the case has filters for every single intake area, including the PSU, which you simply give a little push to and they then pop out for a rinse.
The PCI slots are ventilated as well, so with a card like yours that dumps heat into the case, keeping a slight positive pressure will ensure that the hot air doesn't stagnate and is instead forced out the rear. This area is typically the worst part of a case for airflow, but I would say that the positive pressure + PCI Slot Vents is the best thing next to the Lian Li full aluminum dual-fan PCI Slot Cooler!
Just a suggestion, but there are tons of other great cases as well so look around!