Is this enough for 560ti's in sli?


Pretty sure the GTX560TI calls for 170W. X2 that's 340W. Add in a 100W CPU and 50W for board, drives and ram and you get around 500W. That PSU can do 48A, or 576W. It can do it, but its mighty close to its limits. As Rob said, you probably want to go with a quality 750W unit so your not so close to the edge.

Also, that PSU only has 2 6+2 pin plugs. Make sure whatever PSU you buy has four 6pin plugs to power both cards.
That PSU is competent for the job. Normally, if a PSU doesn't have the requisite connectors, I would not advise using it, but in this case adapters should be safe. If you have any stability or other problems, I'd get a quality 650W PSU with all four PCIE power connectors already present.