I’m running a GT 640. It runs so-so: I tend to have my gameplay viewport surrounded by menus so I can get a silky smooth performance. In fullscreen 1080p it barely runs anything at 30 fps, but that all depends on the lighting, the shaders, the effects, the reflections, stuff like that. The third person blueprint with default settings runs 21 fps with Epic settings in 1080p. Medium settings cuts the resolution in half and lowers other settings as well, and I can easily get 55 fps with that in 1080p.
A GTX 960 would be a godsend. Run everything at epic settings in 1080p, and just don’t care about anything!