Hi Dan. I agree with Darren. Give V Australia a good look and if you can be flexible a little with dates you could get a great deal. I am planning the same trip as you. They have some great fares but also a great plane with probably the best seats for comfort, width and legroom..and good service from what I have been told. Qantas are worth a look too.
United and Delta have great deals going too..though you might want to check www.seatguru.com and http://www.airlinequality.com. These sites have seating arrangements (seat guru) and also passenger reviews of seats and service (airline quality/Skytrax). After doing my research from these two sites and people I know, I think V Australia comes out way in front..but thats from my perspective. Good luck! Tim