On medium with standard textures and not too many mods, 60 fps should be achievable, possibly even a hybrid of high and medium. Keep anti aliasing off, shadows at medium and antistrophic filtering at x16. Shadows and anti aliasing are the biggest frame rate killers. Keep draw distance about the middle and try the rest of the settings at high and see how you get on. Also 600w will be a bit overkill for that system unless you plan on a second card down the line.