400 for an oculus, plus around 1000 for a competent pc? You could probably do less for the PC but at that point you are making compromises that I wouldn't personally make.
If you're going for something like the Rift S which is 2560×1440@80Hz you'd probably want to go up some from that to not compromise on the graphics. The lower resolutions on the other headsets would be less demanding.
