If your branches are thin and whispy looking as the SPS grow, then you have too much. You can also get short stubby ones that just want to encrust, as described above. Whatever the volume, the flow needs to be effective - not all flow is effective. Something like a wavebox moves very little water, but it is effective and SPS grow with very nice patterns and have good PE even down in the shadows that is hard to duplicated in captivity. Back in the early BB tank days, people wore their flow rate as a badge of honor and I am not too sure that all of it was good.
I do use a wavebox since I love the growth patterns that they give with ease - waveboxes are not the only way to do this, just the most reliable that I have used. I also use a few tunzes at half power so that the fish don't have to work too much, but are also not getting blown all over the place.