If your Amex is Australian, then yes, you can transfer 1:1 to Velocity. If US, the best you can do is transfer via SPG but there's a significant reduction in the transfer ratio. You also need to have an Australian address to open a Velocity account.
After 1 January 2015, Delta allows one way award redemptions so you may be best waiting 10 days and then trying to book the seat through Delta.