None of them. They are either running an AMD APU (Which isnt really enough for smooth 1080p gaming) or a low end laptop graphics card.
Even the computers they offer as "gaming" machines are ridiculously overpriced for what they offer and are very unbalanced as a build. Ironically the best they offer is one of their cheapest. Still very overpriced though and likely made of low quality components.http://www.harveynorman.com.au/pryon-pry-gfx8242-storm-trooper-gaming-desktop.html
For the price of $1350 one of the pre-builts is asking, you can build yourself a far superior machine even with Australian tech prices.
If you are willing to build your own, start a new thread with this form filled out.http://www.tomshardware.com/forum/353572-31-build-upgrade-advice