I don't bother running 100, 600 or 900. I can't run them at a much lower voltage than 200, 800 and 1000 so I don't see the point.
I run 4 steps - 200, 400, 800, 1000 - pretty close to standard voltage. My phone runs smoother that way. I can run -200mv at 100mhz, and big UV's everywhere else...