For those who have got NBN but now find the new modem location restricts WIFI range, I have discovered a gem the extend the range of my Archer VR1600 (it is claimed to be compatible with all brands). I tried a few mesh systems, but the best, and simplest outcome was this:
Very easy to set up, and by giving the new network the same name as the current one, it forms a mesh. I gave my 2.4gHz and 5gHz networks the same name, and my devices automatically pick the strongest signal as I move through the house. Range is very good, and price is less than $150 (I got mine for $135 delivered on Amazon AU). Can't guarantee results for others of course, but it's so simple it's worth looking at.