Gaming PC under $900AUD

Hey guys I'm fairly new to computer building and I'm looking for a new intel gaming pc. That can play BF3, COD, Portal 2, Gmod, etc on medium to high to ultra settings.

Approximate Purchase date: about a month

Budget range: 800-900 max

System Usage from Most to Least Important: Gaming, media, surfing the net, business work.

Parts not required: none, i need new keyboard, mouse, monitor etc

Preferred website(s) for websites: don't mind as long as its from Australia

Country of orgin: Australia

Overclocking: yes a bit

SLI or CrossFire: yes

Extras/needs: atleast 8gb ram, 500gb+ HHD, maybe an SSD, need a monitor 1920 x 1080. Also need a keyboard and mouse

Cheers

Try pc case gear, fairly sure based in melbourne not to bad on prices either

But I domy know what to choose that's why I'm asking