PowerStore offers support for UPS, FedEx, and USPS shipping quotes by default. Australia post is supported within eCart but you would need to customize PowerStore with eCart to add support for this shipping provider's quotes to the PowerStore.
You can use Australian currency, the shop is already setup to work with dollars so you would just need to update the USD entries to your currency code.
The payments gateways that are supported are PayPal and Authorize.net. You could make use of eCart to add in other gateways but only if they are supported within eCart. Here is a link to the eCart page for more information:
The demo site that we have for PowerStore is the only one available, are you looking for more information about how it works in any particular way?