The GTX 960 should be right about borderline for VR. According to Oculus, the 960 and 1050 Ti meet their "minimum requirements" for the Rift, but will undoubtedly be making use of frame reprojection to help smooth out low frame rates in many games, and both the Rift and Vive "recommend" at least a GTX 1060 / RX 480 level card. Plus, those requirements were made around the time of the device's launch two years ago, so there may be more games coming out now that push those limits a little more. And of course, if you were to go with another headset with a higher resolution, the performance demands would be higher, though a feature was recently added to SteamVR to dynamically reduce the resolution on higher-res devices if the GPU can't...