you didn't read the article.
the 770 really can't be overclocked more then 5% or so, as it's basically a factory overclocked 680, its really pushing the boundaries of what the 104 gpu can do... so an overclocked 7970 GE will probably match it blow for blow, with almost no difference between them (as there is some more overclocking room still in the GE, particularly the ones with their voltage unlocked)