I'm not sure what spec the transmissions are in Australia. Come to think of it, if the AU spec WRX are the same as Japan, they have 2.0 litre engines.
In North America, the WRX has a 2.5 litre engine, tuned to 227hp. We also have an STi model, also 2.5 litres, tuned to 300hp. We have a 2.5 litre non-turbo Impreza, and those transmissions are said to be quite fragile, but I've always had the impression that the WRX transmissions were more robust. I'm not sure about the transmissions where you are, but ours were only 5spds in the WRX, which I think led to larger gears. Perhaps the 2.0 litre WRX are 6spds? Another thing, we never got a WRX model until the "bug eye" style Impreza in the early 2000s.
Hmm
The model just superceeded is 2.5 Ltr with 5 speed stronger than previous models.. The STI has the 6 speed [close ratio] with 2.5 engine..
Then there's the 6 cylinder boxer engine....
The new model is the same...