Thats not a problem as long as you plug in both PCIE cables from the same PSU to the back of the Apollo, and the PSU has at least 200-300 watts headroom for the Apollo.
Issue come in when you try to plug in two separate power supplies in the back of the Apollo (ie some people think if they have 100 watt headroom in one PSU, and 200 watts in another, they'll just plug in one PCIE cable from each PSU to the back of the Apollo...BTC). Even a small imbalance in voltage will cause major current to flow between the PSUs and melt the cables/start a fire.
Emphasis mine.
Ja. One should NEVER try to run ANY sort of PSU's in parallel. Because they are independent devices they will literally fight each other. You want to run PSU's in parallel they MUST be designed for it (master-slave modes) and wired accordingly.