Definitely MSI Afterburner. I've used Rivatuner before and I think Afterburner is better.
Afterburner would only work for overclocking for me. Setting the memory underclocked had no real effect on it. Using rivatuner on the memory worked tho.
Altho lowering the memory to 600mhz only lowered the temp 2 degrees and 2mh/s faster.