Well the benchmark is simply called "Unigine Heaven" for future reference
And yes, it is quite pretty because its DX11.
You can use a program called Furmark to stress your GPUs and see if they are over heating. Anything over 92C is to hot but lower with default fan settings is quite normal as opposed to what people want to think.
You can also use a program called Coretemp to monitor the max and low of your CPU temp. After you turn this on i suggest Intel Burn Test, WPrime or something similar to stress your CPU to see your max temp under load. If your stock, anything over 80-85c is excessive.
Please remember that Furmark is a stressing program and is meant to completely max and over do your GPUs. Any real game play wont be as bad, especially in a Crossfire setup due to scaling.
If there is ANY throttling due to heat related causes this will show you. If your temps seem to be in the clear then it probably would be something in the background simply hoggin your resources during game play. The biggest culprit normally would be an anti-virus kicking in or something or a port monitor that is monitoring incoming and outgoing traffic.