Well, it is a kit of two 750W PSUs. It looks like each PSU outputs max 750W on either voltage, so you should be able to get max 1500W from both of them.
I don't know how safe this setup is, considering this bolded line from their description:
... Hashboard #2 will be powered using 2 PSUs, to avoid the possibility of damaging the board connect the included fault protection kit to the breakout boards ...