Is there a decent upgrade option from a Radeon HD 5970? I've had the card a while and it's starting to have trouble pushing games.
Been thinking about the 770 or the 280x, but is it worth it?
Either would be a significant upgrade. The 280x is equivalent to the 7970 GHz edition, so it's two generations ahead plus an extra bump. 770 and 280x are neck and neck.