and really, to be able to answer this question properly we will need:Azzab wrote what gaming computer is the best bang for your buck :)
budget?
intentions for use?
need hole system, monitor, mouse, keyboard, tower or just tower?
do you have preference for amd or intel?
$4299 gets you something like this: http://www.scorptec.com.au/system/101
$2699 gets you something like this: http://www.scorptec.com.au/system/135
$1069 gets you something like this: http://www.scorptec.com.au/system/126
you would be able to get the above spec pc's cheaper if you buy the parts from somewhere like http://www.msy.com.au/ and build yourself, they even build systems as well.