Joseph Coulter wrote:

More on the train. 3 nights each way Perth to Sydney.

I like that idea a lot, I've done similar in the US, so I'd feel
comfortable with the situation. I'd take my time doing the trip and
stop off on the way.. I wonder if I can get a rail pass?

Answering my own question, yes they do.

http://www.gsr.com.au/travel-advice/rail-passes.php

Seems quite cheap too.