If you plan on keeping the GPU and upgrading other components (CPU, RAM and so on) later, go for the 960, it will do just fine at 1080p.
But if you plan on just playing a bit for the moment and get like a whole new system next year or something like that go for the 950.
Keep in mind that whatever you choose, the i3 will still be a problem ecpecially in new games and CPU demanding games, because it's a dual core. To run new games smooth you'll need atleast a quad core, preferably an i5 of the newer generations. (4/6)
But a third gen i5 will still do totally fine in games paires with something like a 960.