You would be much better off building the computer yourself. For the price, wouldn't recommended. Granted Australia has much higher prices, you could do much better with a custom build.
Check out my $650 build here:http://www.squidoo.com/electronicandmore
Switch the 6870 with the cheapest 7850 in Australia and you'll be more than solid.
Price when converted to Aust. prices, the total should be around $750 before the OS. Build your comp is easy honestly, check out Newegg's build guide:http://www.youtube.com/watch?feature=player_embedded&v=4CStOC0hET8