Don't use a door to door courier such as TNT or DHL for something like this - unless money is no issue.

Search for air cargo agents / freight forwarders and get a quote (make sure you have the weights / dimensions of your luggage to hand) , this will work out far cheaper. You'll have to bring your luggage to cargo hub in Melbourne, and it'll come straight to KLIA Cargo terminal. You have to do custom clearance and the other procedures yourself, but it'll work out a lot cheaper.

Eg. last time I shipped a bike from UK - TNT or DHL would have cost me around £400 (volumetric weight was 49KG) and that is with my 50% courier discount. Air Cargo I managed to send for £140, and the clearance and handling charges at KLIA Cargo were RM60 only.