I think your scheme

Starwood AMEX ---> Qantas ---> Oneworld

is about as good as one can get barring any short-term or one-time promotion.

In terms of value, I estimate that the scheme works out to be a "rebate" of 2.4% per $ charge based on the way I might claim the award (coach RT air tickets SFO-HNL).

However, HH AMEX maybe a better deal if what you want is free hotel room. (Kind of drifting off the topic...) I can get ~3% "rebate" using that card.