Need opinion on gaming build

Looking good, if you don't got plans on going SLI a 600W power supply is more than enough. Got almost the same setup myself  

Links are not working. Good build. If the prices are just average you may want to get a new z77 board and a Ivy Bridge processor. If you already have the rig then you will still kick butt with it.

My only big issue is the PSU. Personally I have had bad experiences with CM's PSUs. I prefer Corsair, Seasonic, SOME antecs

Looks rather sound to me. The only thing I can't comment on is the PSU since you didn't have the model number and the links are not working. I did a check on newegg and they do have a deal on the 500R case and a AX650 650w power supply which is a high quality power supply.

http://www.newegg.com/Product/ComboDealDetails.aspx?Ite...

One more note, if you are going to overclock may I suggest an after market CPU cooler as the stock one just plain sucks for overclocking. Something like the COOLER MASTER Hyper 212 EVO should fit your budget.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Check my sig  

the PSU is a coolermaster gx 750w
Im also from australia, i don't know if newegg ships products to australia.
Also, if i were to choose a Z77 motherboard, which should i choose that's as good as the motherboard my friend chose for me?

I would rather not comment on a Z77 since they just came out but Anand has a good roundup they may help you pick features: http://www.anandtech.com/show/5728/intel-z77-panther-po...

http://www.pccasegear.com/index.php?main_page=product_i...

what if i changed the motherboard to gigabyte G1 sniper m3, is that better?