I never used the SLI capability when it was my main computer. I have four displays connected and SLI is not available when you do that. When I put the computer aside I enabled the SLI, but have nothing to use it on .Looks like it's already running a SLI system. That power supply should easily be able to handle two 960s if you decide to really go crazy with the folding habit.
Edit: It looks like you have a very good cooling setup too.
The cooling was barely adequate. But then there are temp sensor issues with that MB. So it was really hard to tell where you were at with that board. They changed the monitors to drop the temp displays some 20° but 3rd party programs were not fooled with that. For me that was the major flaw in that computer build.