Probably a bit on the expensive side for your budget but the canon EF24-105mm L IS is a magnificent lens for (grey) $1100-00, not too many others that will beat it. Also the EF300 f4.5 prime for telephoto shots.
As I said, above your budget but these are both lenses you will have for a long, long time and the early investment now will pay dividends in the long run. The A$ can't stay this high for too much longer and the purchase now could see massive savings in the future???
Richard