PSU wattage calculator
^ Use that calculator to specify all the components. I gave in the Athlon X4 630, 2xDDR3 RAM sticks, 2xSata 7200 RPM HDD, 1 ODD, HD 5770, 2x80mm fans , 2x120mm fans and it gave out a 400W figure with 100% peak load, keeping another 25% headroom for safety, the vx450 would...