This system only needs a 600w PSU (AMD CPUs are power hungry). You could drop down from 750w to 600w unless the extra headroom is for Crossfire.
Also fx-6300 is probably better than a dual core for gaming. Stick with that AMD CPU unless you want a Intel 3470 instead.
8gb RAM should be 2x4gb. I can't explain why but I heard it's better.
Lastly, some parts of Australia get really hot and overclocking adds a lot of heat so get a special cooler such as a cooler master evo.