It's not the same card, the powecolor has two normal 7970 gpus, the asus ares II has two 7970 ghz edition gpus in there, with a higher grade pcb and better cooling system, the reviews shows it outperforms it in every way, performance, noise, temperatures, overclocking.
And it's a limited edition of just 1000 cards, not 100, the powercolor is also limited, and not official the same as the ares, the fastest official single card dual gpu is the 690 GTX.
Keep in mind those cards are dual gpus, for single card, single gpu, the fastest is a 7970 ghz edition.
But this is irrelevant to the op, for a person who has a 610 gt, i don't think high end cards are an option...
A 7770 from amd or a 650 ti is a good option for low budget card.