+1, except the Corsair 650TXV2 doesnt have enough PCIe connectors to SLI GTX 560 Tis. Altho still a good choice if dandrews is willing to use peripheral to PCIe adapters.
The XFX XXX Edition would be my choice for an SLI PSU.
I would go with the Corsair as that is my preference and it has higher wattage. It also has a single 12v rail which is good.
It doesn't really have the higher wattage, as the Antec BP550 Plus has 534 watts available on it's 12V rail according to the label. 40A for the Corsair only equates to 480W. The Antec also has higher rated 3.3 and 5V rails.
I don't see why a single rail is an advantage in this case, unless the Antec BP550 Plus has poor rail distribution or something.