Buy the Antec Green 500W unit ! The lower end CM units are crappy with one exception the GX450 which isn't enough juice and PCI-E connectors.
The only other good unit is the THERMALTAKE TR2 700W-NON MODULAR (TR-700PCEU)= expensive.
What's wrong with GX 550W, which should be sufficient for GTX560Ti if not SLI I believe. This is decent but affordable PSU from CM.