I'd suggest playing with the angle of the fan you have blowing on the GFX cards to see what works best.
If your environment is such that getting down to 75 degrees with less than 100% fan is impossible with stock settings, I'd suggest underclocking your card. In my experiments, I've decided that dropping voltage has a better effect cooling the cards than dropping MHz does. That said, in order to run stable on lower voltage you need to drop MHz as well.
I'd suggest setting your Memory Clock as low as MSI afterburner will take it, and then gradually drop your voltage 10mV at a time. After your system locks or crashes due to insufficient voltage, reboot and set voltage 15-20 mV higher than the unstable settings. Make sure you're mining during the tests. If you want to go cooler, just drop the Core Clock a bit and repeat the process. But don't expect to be able to drop the mV more than about 10% unless you seriously underclock.
In my humble opinion it would be more cost effective to run your equipment underclocked yet cool and fans less than 100% than to try to pull as much Mhash/s out of your setup as you can. You might make a bit more money in the short run that way, but in the long run you're just going to end up with a bunch of useless computer parts.
Thanks, yeah i played with all the settings. Even with memory at 300mhz and core at 550mhz (lowest), the thing is still 90+degrees. The only way i can get it to 80 is if i stopped mining one of the gpu. At 550mhz, it's only doing 230ish mhash, which kind defeats the purpose of getting a 5970.
It wont work long term. I ordered a pcie extender and a utility blower fan. Will try it out. My other card(the one without the fan getting blocked) is only at 75 degrees with a 850mhz overclock! so looks like the issue is definitely the blocked fan.
