, your PSU is of excellent quality, and IF
you do not intend to overclock either the CPU, or the GPU, and IF
you never intend to by a second 560 for SLI, then yes, you can get away with it.
Nvidia, bare bones minimum requirement for the GTX 560 is a 450 watt PSU.
GeForce GTX 560 | Specifications | GeForce
Personally I wouldn't consider anything less that a high quality 600 watt supply.
HAF 932 Advanced / Corsair AX1200 / Asus Rampage IV Extreme / i7-3930K / H100 Cooling 4x120mm
16GB Corsair DDR3 / GTX 580x2 SLI + GTX 460 PhysX / SSDs Mushkin 240GB, Crucial 256GB, Crucial 512GB