As I stated above the issue would only be apparent if all your graphics cards were actually under full load. I don't know enough about 4 way crossfire to say if that will happen or not.
If you read the links in my first response you see the XFXR7970 only draws 25W at idle but can draw as much as 315W under full load. Even under full load the Enermax linked above and below should be able to keep up with the demands. It is rated at 1475W.
If you can exchange the power supply the unit linked below would be a better choice with less chance of anything happening. You may still need to use an adapter. There are motherboard power connectors provided but they may not be 6 pin but 4 or 8 pin.
Below are 2 additional links to Silverstone. The first is to the specs. The second is to a list of supported GPUs (graphics cards). You will note that PSU only supports 3 of your cards.
I recommend you consider the Thermaltake linked below. There is a discount promotion that ends today. Really a good price for a superior PSU.
From your other recent post I see you deal with newegg.com. If you bought the Silverstone from them I think they would exchange it.