Running 2 EVGA GTX 560 Ti SC in SLI, Asus M4N98TD-EVO mb with 1 slot of space in between them (slot plate removed to help exhaust air) so it sounds like I have more room between the cards.
I have an Antec P-160 performer case modded with a ducted 170mm Xigmaqtek fan blowing half it's airflow to the bottom card the other to the rest of the case. 120mm in the front with a 92mm in front of that for just the gpu,s Corsair H-70 exhausting the cpu heat (that alone dropped case temps by 20 deg F), Corsair HX750W psu with a 120mm fan and a 140mm Xigmatek in the top of the case exhausting. Running F@H temps are 62 deg C bottom, 46 deg C top with ambient @ 74F or 24.3 C Gaming sees both at around 66 C to 70 C so proper airflow makes a huge difference. Pic attached.