How much performance do you want, or need? That's a 3 generations old card, and a current midrange card (i.e. 7750) is about 20 - 25% faster.
I would not get anything less than a 7770 though, but a comparable card today is a 7850, or a 7870 since you've got 2 of them.--
Wacky Races 2012!