My personal experience is that, yes, I'm getting something much closer to what my wife does when we do the same weight-lifting regimen together. (Before, I had much less trouble developing "flashy" bigger muscles, though I never could out-lift her.) I can still train my muscles to the point where it's possible to lift higher weights, but it's no longer possible for me to get beyond a "lightly toned" look these days.
I don't take spiro, though, so I have no idea about that.