Originally Posted by slaWter
Good airflow can also get in the way. Quite a few custom cooling solutions or also the cooling design of the 6990 push the hot air out on both sides of the card: out the front out of the case but also out the rear right back into the case. Quite a few, also highend cases with good airflow, have a fan right there to cool the video cards. So in fact your case is working against the video card cooling and that has a very negative effect on the GPU temps of course.
Unfortunately, my Palits also use such a bad cooling design. That's part of the reason why I had to return the third 580.
Your two fan cooling suggestion would suffer from this problem as well.
Tri SLI/CF always suffer due to the proximity of the PCI slots, one of the cards will be more baked than the others pretty much regardless of what you do. A lot of heat gets dumped in the case though but i wouldn't say that the palit's cooling design is bad,if you use just ONE card in a well ventilated case the gpu temps will be lower than the standard cooler. It's not a good sollution for Tri SLI though, thats for sure.
The cooling design on my MSI twin frozr 580 doesn't exhuast air through the backplate either but it's the best card i've had for years in terms of temps. Idle temps are under 35 c and maxtemps are 20 c lower than the 470 i had before and that's with the clocks at 835/1670. Cpu and system temps remains the same as with the 470's reference cooler, i think i could add another card like the first one and still have good temps but a third is out of the question eventhough this case has great airflow.