Yeah i do try and keep up with what's happening re-trails wise and back in the early days (Before i got a mortgage and all that fun work stuff) I was active in the cradle coast mtb club and did a fair bit of trail building and helped with running our dh events.You lucky bastard. You live in Australia’s MTB Mecca. Just in case you’ve haven’t been paying any attention check out videos of Derby and Maydena to see why the rest of us wish we lived in Tasmania. With trails like that only a few hours away you are almost certainly going to want a capable bike fairly soon, so either go cheap and be ready to upgrade if the bug bites, or just get an enduro bike straight away.
I am thinking it'd be best just go with the 4-5k range bike and get something that should be very capable but at the same time also look out for a 20-21 model bargain if it can be found.
on the last currently is the commencal meta am, nukeproof mega290, or something from trek but not sure what, ex7 slash7?