An update on this - our connection with Aussie Broadband happened without a hitch.
Intelligently, the salesperson suggested we start on a 25/5 plan, get them to do a line test once connected and then choose to upgrade based on our actual router stats.
Our FTTN connection is capable of around 83mbps at its peak, so we've bumped up to a 100/40 plan. (A bit annoying that we pay the same as people on FTTP, but get 20 mbps less, but that's NBN/The Government's fault)
The connection has been consistent so far - we've ditched Foxtel via satelitte and now get Foxtel through Foxtel Play and a Telstra TV - streams without a trouble at all.
The router we bought through Aussie Broadband ( Netcomm NF17ACV ) has a great 5ghz network, but the 2.4ghz is pretty rubbish (though we don't know whether it's any better or worse than our previous routers, because we were on slow ADSL1 speeds anyway)
Overall, Aussie have provided great service and our household of 4 millenials is pretty pleased!