Same PSU I have, in fact I have the same GPU as you. Running an ivy I7 with three hdd's, able to OC no problem. Shit ton of fans running for watercooling and all that no problem. 850 watts might be overkill for some, but for a single rail, the amperage is hard to ignore imo. Even my ram is using more volts then it needs, because fuck it, overclock all the things. I paid around 80 U.S. dollars for my PSU on sale a year or so ago, not sure on Australian amount. No complaints from me with my PSU, or GPU.
i dont realy think that this is a powersuply issue. i rather to believe that this might be just an issue with the card itself. But you could double check the wires, if there isnt any damage or a loose connector.