Mate I reckon be safe and just get a sri. Keeping in mind your in melbourne and you guys get a bit of rain. You dont want to be worring about hydrolocking your car EVERYTIME it rains. My mate hydrolocked his car last month and let me tell you its a headache you can do without. You may loose a bit of HP with heatsoak, that can be fixed, but you dont want to loose your whole engine.