Ram and videocards are expensive, however good upgrades from your videocard are REALLY expensive right now. So I'd go with the i5 8400 and 16gb ram, under the assumption you won't be upgrading the videocard any time soon. With a 960 there's no conceivable gaming scenario where you will wish you had the 8600 instead but there are games where it's nice to have more than 8gb system ram and there will be lots more games like that soon.