One tip about opening an account online with Citibank Australia, which is not in the information they provide you.
You must send them a completed IRS W4 Taxpayer ID form, along with the Australian forms they request.
The IRS requires all US banks to collect a W4 Form from all account holders -- and this US law also applies to their foreign bank subsidiaries, such as "Citibank Australia" or "Bank of America UK", when opening accounts for US citizens.
This does not apply to foreign owned banks, such as HSBC, even though they may own a US bank subsidiary. HSBC USA will require a W4 from you, but HSBC Australia or HSBC China will not.