Another thing you might want to test is turning off aero. When running a 4th mon on the sli configuration it will double the amount of vram needed for those effects. I personally run 1 over 3 with 580's in sli and a 210gtx driving my 4th monitor, I put anything that requires vram that I want to see on that card cause I only have 1.5GB of vram and many games will max it out or come darn close. The 580's will NOT run a 4th monitor anyhow, but since I encounter high vram loads in many games, this makes logical sense to me that the 4th monitor would use up these resources and cause a dip in your FPS.
Also I do NOT recommend running MSI afterburner. I use EVGA's precision X and it's pretty much the same program just with a different skin. The reason this is not recommended is because I found it to cause problems with many games that I play like Skyrim and Sleeping Dogs. In Skyrim the sli would stop working and only 1 card would be running at full tilt and in Sleeping Dogs it just wouldn't boot with it running. Thus just don't deal with it and use GPUZ instead, it will only show one cards info but if you're only worried about temps, use speed fan.
This is how everything looks with my current configuration.
http://i.imgur.com/aEyCljD.jpg