Is the PSU able to handle this build?

^And even if you were, amperage is more important than rated wattage when it comes to higher loads like SLI.

A single 970 is claimed to require roughly 500w sys power, but in reality only 28 amps. The rule of thumb with dual card SLI is you use 1.5 times the power required for a single card, which would be roughly 42 amps.

That PSU has 53 amps on the combined four 12v rails. The reason wattage is the more deceiving measurement on PSUs is it's stated conservatively to account for the many PSUs that have low amperage for their wattage.

So basically, even though you don't plan to now, you COULD safely add another 970 on that PSU at some point. And being a gold rated one, it should be able to handle continuous load pretty well.