I just tried reaper configuration you provided on pic.
My system is:
OS: Win 7 x64
Drivers\sdk: Catalyst 12.6, sdk 2.6
Card: 7970, 1160mHz core, 1400mHz memory
Reaper: reaperv13beta4_64

The only difference I see is memory frequency (1850 instead of my 1400). The result is 385khash\s for 7970 and the weird thing is that my 7950 (1000mhz core \ 1375mhz memory) gives ~600khash\s, so I don't expect that increasing memory frequency will give much influence on the results, but I will try to check it later because it requires overclocking.