I have that same 216 watt unit and have been running it now for 1 month. I was using Current USA's 380 watt Orbit Power Compact fixture. I have been yielding better results with the Nova T5 with less heat output and much less wattage. I have a 75 gallon tank and supplmented with several Slimline Aqua Light T5's to get a little more light. For your 55 I think this fixture would work fine for most corals. The only thing I can see needing additional light are some of the light intensive SPS
corals such as Super Color Acropora.