I have been running a few tests on my Evga superclocked #480 and my Evga #295 Co - Op.The problem I am having on various tests with fan speeds all the way up and down on the 295 is that it runs about 10 degrees hotter than the 480. the only test where the 480 was hotter was when I was playing Far Cry 2 on max settings for an extended period of time.Of course the 480 is a better card but a friend of mine was having the same issue with an almost identical set up(except he has a i-7 930 and a Gtx#470).
The coolers for the dual planar cards aren't that good so I suggest cleaning the card if it has seen more than a few months use. Trust me there is dust hiding inside the cooler. Is there any space between the GTX295 and the GTX480?
Turn the fan speed up on the 295, the heat from the 480 would be making things worse