When you've made up your mind on which model to go for, check out the current prices on each around the net.
The $AU is high atm.
I like dealing with these guys.
http://www.d-d-photographics.com.au/
They currently have the 40D body only @ $1389
The old 400D is down to $720, this will probably be as low as it will go since the 450D will be released soon.
But the prices do fluctuate.
Check around.