I did a post on using MSI AB last year which is still pretty relevent (link at the bottom)
Things have moved on slightly though, I wouldn't use furmark anymore (there is some code which disables power regulation in the cards and causes more volts to be put through the core). Any other of the benchmarks above would be fine.
I would also change the fan profile - I'd have the line running up from 40C to about 75C. These modern cards run cool anyway - especially the non ref aftermarket branded ones.
When it comes to upping the voltage you will find that there are diminishing returns. To begin with just push the core mhz until it produces artifacts or crashes, then try upping the memory. It's the same as cpu OCing here - better to have a faster processor speed than raster memory.
Note that you will need to restart your pc to eliminate artifacts - simply turning down the mhz will not eliminate them.
When you hit the limit on stock Vs (maybe around 1050-1100mhz) push up on the slider and carry on with the tests. You'll find that for each incremental voltage increase you get fewer mhz out of the card.
For reference many of the factory overclocked 7970s have 1.175 set at the core so I would start there and see what you can get. You should be fine with 1.2V too if you want to squeeze even more out of them.
Basically just add 25mhz to the core until it eaither crashes or you start getting artifacts in the benchmarks. Then put it back to the last working setting and increase in 5mhz increments instead.
Once you reach the GPU limit then do the same for the memory and shader.
Personally I assign 2 profiles to AB for my cards and never set AB to automatically apply an overclock on start up. One profile is the stock profile (or even an undervolted/underclocked one if you want to be super kind to them) for general use like web browsing etc. Then I have the OC profile which I select and deselect before and after a game (if my cards need the boost). It's the same deal with the cpu really - no need to crank on the OC if you don't need it.
OC Thread -
http://forum.overclo...post__p__450543
MSI AB manual is a useful read
http://event.msi.com...er%20Manual.pdf