According the GPU Hierarchy Chart listed here at Tom's, there is a 3 tier difference between the GTX560 and the 7870 which, if I remember correctly, is the minimum difference to be considered upgrade-worthy. So, yes it would be worth the upgrade.
Other than that, both Friar and Ringo have (gone above and beyond and) pretty much spelled out everything else for you.
Ball is in your court - make a decision!