tbh that OCX ZS series PSU is junk. the XFX 450 will be plenty if you decide to OC that 8320 after getting a cooler esp. since you are looking for a cpu heavy tasking, not adding in a high end gpu. and sorry that 7750 1 gb is really just a bare bones kind of gpu but the budget wouldn't allow a 7790 2gb that would cover any light weight gaming; yeah that XFX 450 watt PSU will also work with a single 6 pin gpu.
edit: and i think you'd be better off with 1866 speed RAM . .