what is your processor? also do you want 250 FPS? or want to spend up to $250? for that price range, ad 960 is overkill and a R9 280 is also overkill, but you might need a better power supply and CPU if you want to run such cards.
on what game do you want to acheive 250 fps. and what screen resolution will you be playing on, how many screens will you be playing on? whats youre cpu? what settings do you want to be playing on. be sure to answer these in your description as it makes it easier for people willing to help you to understand what you need.