You cant go wrong with the 8" gso dob.
It is quite simply
the bargain scope in Australia right now.
You get good optics on a sturdy mount which are the two most important things.
There is room for improvement in the mechanics of the base, but the fixes are cheap and simple for anyone to do
If you can swing a few hundred extra, consider the 10 inch.
I would only buy the 12inch if you never have to transport it as the tube is longer than most cars are wide.