Well, I don't know the prices of graphics card in australia so, I converted to EUR and checked what you wanted to spend, and I only checked prices here in Portugal (that's where I'm from
), which are usually more expensive than other places I've checked like German, France, USA, Canada, etc..
What I advise you to pick is a nvidia 6600GT or if you want to spend a little more the 6800GT since these cards support SM3.0 (Shader Model 3.0) and I don't think that there's any ATI card for this price with SM3.0 which allows you to play games with a more detail in graphics.
/ 
