OCC rates this card with a Gold award for its good mid-range performance and nice set of features. However, the reviewer does note that just a little bit of extra cash will buy you more powerful cards.
"When it came down to the overclocking of the Sapphire HD6790, I was able to get the GPU clock speed all the way up to 1000MHz, which is about a 19% overclock on the GPU core with no voltage adjustments. I was able to get the clock speed a little bit higher, however it was not stable enough to run all of the benchmarks in the OCC benchmarking suite. The memory was a little bit more tricky to overclock on this card, I was trying to get up around 1250MHz, however anything that I set above 1235MHz was unstable and would give me artifacts on the screen, so I had to back my clocks down to 1230MHz. That is, however, about a 17% increase on the memory. Overall the overclocking of the Sapphire HD6790 was just like any other video card when it comes to the clocking with out using an voltage adjustments."