Cheapest I've seen one of these. With the 20% off they are $439.20
It's also possible to price match noel leeming or JB hifi at $529 and still get the 20% to bring it down to about $423.
If you've not had a new account you can get another $10 for registering before the 20% to bring it down to $415.20.
Unfortunately welcome 10 doesn't seem to work on the Xbox so the $10 was the best I could get to apply.
Original warehouse stationary deal: