Motherboard supports SLI, so no problem there.
While the RM-650 isn't ideal for SLI in general, it's a fairly decent unit and has the required connectors (4x 6+2-pin PCIe). It should be able to provide the power for this specific situation. The MSI GTX970 will requires about 150-200W under load (tests at bit-tech and Guru3D), so should be okay.
Only potential problem is if you overclock everything and burn both the CPU and GPUs at the same time -- that's the only way I'd see it getting close to the limits of the RM-650.
Other possible issue is whether the case has enough room/cooling capacity for the two cards, but case isn't mentioned so can't really tell. Edit: Case is large and roomy, should be no problem there either. Just check the GPU temps are okay under load to make sure they're getting enough airflow as there's no possibility of a side-of-case fan.