Out to Horsham today to look at rental properties again, and while we had to wait between appointments we decided to check out the local thrift shops to price furniture (which was a dismal failure). I did happen upon an ADSL2+ modem for nine bucks though, and to my surprise it works rather well.
It took a bit of finagling to get online - apparently Telstra had changed our ADSL password and I'd written it down, but not in the usual spot and was still trying the old one. It synced to the DSL quite quickly and the numbers look rather good for rural internet.
After about 30 minutes of pings, we'd lost about 6 packets (which is bugger all, and most likely due to the WiFi, not the ADSL) and ping times were reasonably stable (one went over 2s but that was an oddity). That's a far cry from what the other modem does, which I bought brand new by the way. I don't think I'll ever bring myself to buy another SoHo Cisco/Linksys device again.