If I buy the TP-link (more common is now for 49 $ the 8951N
8950 is much better than 8951 which is trendchip.. do not buy them..
8960N is still only $45 .. look on ebay or MSY or Centrecom.. You must buy the exact model.. not the 8951 or 8961 because they are not the same hardware.
Latest MSY pricelist shows 8950N for $33 and 8960N for $42.
The Sagemcom is ok.. just a massively large and power hungry device when you need a tiny little unit.
I posted the bridge details on my website.
https://sites.google.com/site/lapastenague/a-deconstruction-of-routers-and-modem s
See the pdf down the bottom.
All of this is assuming you are on ADSL with Optus and can use PPPOE client in the TC..
So you simply do the setup of the TC go to the WAN setup and choose pppoe.

Put in your account name and password for your Optus login. Service name is not required.
In my experience it failed miserably.. so be warned.. PPPoE is not always successful on the apple router.
You create a wireless network.

You can then use extend wireless on the extreme to improve the wireless coverage.. but the Extreme still needs to be near enough to the TC to get good signal itself.