Not a bad PC - and if it's better than the one you've got - it's an upgrade
However, your 305watt Power Supply Unit might be powerful enough, but how old is it?
You're OCing your CPU which uses more power, and if it's a year or more old, take 5% off it's total wattage for each year you've had it.
The Power Supply Unit is the one component you don't want to cheap out on.