Dual Radeon HD 6870 one cooler than the other

Hi,

I added a second Asus Radeon HD 6870 video card to my box in an attempt to have a cooler and quiet 8 monitor experience, after replacing a Dimond Radeon 6870, which was overheating all the time even with the fans raving at 100%...

So in the beginning I had the two video cards right next to each other in adjacent PCIe slots, and I noticed that at equal Fan Speeds one stays at 39C while the other at 45C temperature. I thought that the top one is somehow blowing back heat at the one below and set them apart one PCIe slot away, so that there would be more air in the middle to dissipate the heat. When I measured the Temperature again, nothing had actually changed...  

What is considered an OK video card operating nominal temperature? Is up to 50C OK or should it be kept under 45C for example?

And my other question is: There is this FAN Cooling software called Smart Doctor - it comes with the ASUS Radeon HD 6870, that allows you to setup Temperature levels at which to rave the FANs at corresponding speeds. The thing is that when you install it once for the first Video Adapter it is not smart enough to recognize that you have two adapters not one, and provide means to control both, the way the Catalys Control Center does in the ATI Overdrive sub-option... Does anyone know of a way that you can have two instances of Smart Doctor that would control both Video Adapters simultaneously???

Thanks,

Tom