Go with the first option, the GTX 960 or the R9 280X and the 8 GBs of RAM. As to the question which is better the 960 or the 280X, they are almost completely equal (with the R9 280X beating the GTX 960 with some 5%-10% performance), although there's a limited time offer during which you can get a free copy of The Witcher 3 if you purchase the GTX 960 as a component (I am not sure if it's offered in pre-built computers).