Originally Posted by RichardMEL
Remember if you decide to go for a pass (QF only) you must buy it *before* you enter Australia, and also note I think they restrict the sales of said passes to a tie in with an international tix into Oz - ie: I think you have to fly QF (or possibly a OW partner?) into Oz to tack on the airpass.. that may not be the case though - call your local QF res office to find out the exact cost and for any gotchas like that).
DJ (Virgin Blue) only has a tenious codeshare agreement with UA, but it's not very relevant to this situation. Best bet is, as the others have said, is to trawl qantas.com.au, virginblue.com.au & jetstar.com to find low fares on the sectors you're interested in.
AFAIK, it's not strictly necessary to fly QF (or OW carriers) towards OZ in order to buy QF pass for domestic legs. BUT (eheh), the pass' rates change heavily.
The cheapest fare is for passengers travelling to OZ with QF. If you vchoose *A, you'll pay more than these.