Via the Flight Deal Virgin Australia has New York – Sydney for $675 in August and September.
There’s a 10 day minimum stay (meaning you can return 10 days from the day you leave, not the day you arrive). Miles can be credited to Delta or Virgin America but will not earn full miles flown with either. You earn 20% redeemable miles with Virgin America but 50% redeemable miles (100% elite qualifying miles) with Delta.
Here’s a sample itinerary:
This should be bookable through most online travel sites.