I went to PAX in melbourne a couple of years ago. It was ridiculously large compared to supanova, at least based on my experience.I didn't even know there was a PAX in Australia. Is it open to the public? Never been to a gaming convention. Might go as it's in Melbourne.
Honestly if you can stomach the crowds it might be worth it for computer parts alone, I remember when I had gone they were selling graphics cards for way cheaper than places like umart (I think the biggest difference I saw was like a full 400$ cheaper at the time or something along those lines.
On a separate note, if I'm ever going to get games day one, I might start buying from Amazon.com.au exclusively, days gone currently going for $52 as a pre-order which kind of blows my mind.