Agreed, MP40W. I have the MP20 on my LPS 58 using short pulse (wave) and it's JUST enough, sometimes wishing I had a little more. If you used some of the more intense programs (reefcrest, etc), it might work a little better. If you're going to do SPS, there's no question what so ever (and you might even consider a second and/or other type of supplemental flow).