Third-Party
Looks like both United and Qantas/American Airlines are having sales on flights to Miami. I've been following these the past week and just a few days ago prices were around the $1800 mark.
Qantas are probably worth the extra $100, but United are still a pretty good airline.
I believe you would earn 160 Status Credits on the Qantas flights, though QF flyers feel free to correct me.
Personally I'm hoping Virgin Australia/Delta get in on this, and will be waiting until Monday to book on the chance they join in. Otherwise I'll gladly take the QF flights!