Well more light penetration is just common sense that yes you WILL get more yield, but veg them longer and make sure they are healthy to see a REAL yield difference. Just throwing the same veg time plants and similar plants just changing amount under the light will yield tad more but doubt you notice.
I just pulled 9oz dry in zips off a chemdog under a 600 with 3 other plants fighting for that light, don't know if that's "enough" for you but it is for me.