IF you are able to get a visa to work in Sydney, then I would do that, hands down. I used to live/work in Brisbane and it's a lot different than working in the US. It was a great experience and I made one of my best friends through work there. In fact, if work here was more like it was there, I wouldn't be so hesitant to go back into the work force (I've been a SAHM for the past 9 years).
But, finding out if you can get a visa to work in Oz should be your first step. Remember also that they take out a lot more tax in Australia, so just because they pay more, doesn't mean you will take home more when considering 65k vs 50k. Probably about the same. Though, that never bothered me. I always felt I could see a lot more of my tax dollars at work there in terms of infrastructure/public spaces/amenities/city cleanliness/etc than I have ever seen here.
Personally, I feel strongly that regardless of the possible negative (and this is relative), short term, impact on your finances, an opportunity to live/work in another country is always worth it!
And living in Australia is totally worth it! Best of luck, I miss it. A little jealous over here!