The AA(Australian) site (as in
American Airlines | Airline Tickets and Airline Reservations) does have good pricing. They've improved it since it first came into play, but it doesn't have the same flexibility of the AA (US) site.
You can put your QF FF number onto a booking at either site.
For my current situation, I've now tried fudging things a little and I live in the Suburb of Australia in California, postcode 0xx_x. This didn't work a few years ago, but I will see if it works now. The other option is to put the booking on hold and call the Oz Call centre - but I've seen reports that a $60 fee can be charged - ie more than the Amex conversion fee I'll pay.
-- Edit: Status Ticketed <date>. Phew. It does work! (Now to see if there are any immigration issues!!)