To overclock the Powercolor card today we used Catalyst Control Center.
Sadly, there was not much headroom on the GPU core, achieving 970mhz before the system would hardlock. The memory was a more positive experience as we managed to increase it from 1425mhz (5.7Gbps effective) to 1605 mhz (6.42Gbps effective).
A sizeable increase thanks in part to the massive memory overclock we achieved.