Hi, Nicola - welcome. I've not hiked in Australia, but we've got several persons here who have (Franco pops to mind immediately.)

To get better answers to the question "which pack?" it would help to know what the rest of your load looks like, perhaps by giving us your gear list. If you know, it would also help to know how much capacity the load takes up and how much it weighs.(Will the Blaze be too large? too small? or do you know?) It might also lead to suggestions on what not to take, which would affect the type of pack you'll want.