Intel Core i5-750 processor, critique my specs?

You don't need to change anything, your PSU is just fine the only time you're gonna even consider getting a new PSU is if you plan on going SLI (or running more than one graphics card) I'm sure you've seen it advertised on your NVIDIA Geforce 9800 as it is SLi compatible. When you do plan on upgrading your PSU the 500W should be find but just get one with more Watts 600 - 800 should do.