Hello looking to upgrade my graphics card but not sure what is a good upgrade

i got a asrock fx extreme 3 board. running a nvidia geforce gtx 560 atm and looking for a new one. wich graphics card would be best to run to be up to date and still in capacity of the board.
happy to update ram to max wich is currant two bars of corsair vengeance.
not sure whats arround on grafikcards so need some advice please.
thank you