Well then, if you can afford the 580EXII - go for it
It's got the power, good swivel head, ETTL master capability, PC sync port if you ever want to radio slave it, build quality etc.
As for where to get it from, I've found
http://d-d-photographics.com.au to be one of the cheaper Aus based online shops. Think they've got a store here in Bris now, too. Might save you postage costs if you can pick up.
But usually I find cheapest option is to buy from
http://www.bhphotovideo.com/ or
http://www.adorama.com/ or even amazon in the US. Even with the terrible exchange rate at the moment and slightly higher postage costs, you can still save a worthwhile amount.