For $300 - $400 Aus you will be flat out getting a halfway decent new refractor (went through this process at the start of 2004, yep guys I bought two new telescopes in 1 year, warning Jimmy when you get hooked you get hooked
) and if it is decent then I'd be really surprised if the mount was suitable.
Have a look in your local Trading Post newspaper if you want a refractor. They will take more (relative) abuse than a reflector so the chances are if a 4 inch one comes up for sale it would be ok, as long as it doesn't have anyobvious dings in it. But as everyone else here has said, "more bang for the Bucks" get a reflector.