Since you've already got the vodafone account set up i definitely think you should get the phone somewhere other than a vodafone shop.
If your in auckland theres a real good shop on constellation drive off the motorway called Parallel Imported (dont be put off by the name!). They have a huge range of all brands of phones and have massive savings on them. I bought a nokia 5140 from $420 from their before it even hit the shops in auckland and even now they are still being sold for $600+. Plus all their phones have 1 year warrantys that can be extended.
As far as choice goes ive always been pretty faithful to the Nokia's. They seem to have the best features but mainly the reliability of them compared to the rest is really good. Otherwise i would have to say SonyEricsson are really up there now and have some real flash phones.
With that price range of yours in mind im sure you'd find what you need there, goodluck!