I don't think of the psu has part of "a build." You get a ten or twelve year psu, it's going to be serving you in two or three builds, most likely. Your needs will change and likely grow. If you think of it this way it makes sense to spend the extra $60 or $70 and get something like a Seasonic 850 or Corsair equivalent.
Because it's not just about having "room to grow." It's also about having your current build protected against one of the most common sources of system damage, a failing psu. A good psu is cheaper in the long run.
Greg N