Good on ya mate, can you get us pics of the giant kokopu? Chillers are definitely worth the investment, fortunately you're going into this hobby over winter so you'll have a bit more time to get one as you'll have less difficulty in keeping the temperature below 20*c, however you'll need a chiller come summer.
On that note though, if you're serious about getting into natives, then you should invest in a decent size chiller that can accommodate tanks of a reasonable size, they often come up on trademe for reasonable prices, else you can buy em overseas.