400 watt 20K over a 75?

[ros_sco]

I currently have 3 x 175 watt MH and one 95 watt vho actinic over my 75 gallon 48x20x18 reef. 1 x XM 20K that runs from 9 am to 9 pm, and 2 x Hamilton 14k that run 10AM to 6PM. Actinic runs 8AM to 10PM. I am seeing excellent growth. 90 percent of my corals started as frags about a year ago. I am not sure if lighting is the answer, but I am really interested in bringing out more greens which seem to fade in my tank. Blues and pinks and purples are awesome in my tank, red and oranges are ok, greens are a bit yellow compared to other tanks that some of my frags have come from. A coral can be intense neon green and over time ends up like what you see in the picture. Namely the green slimer in the first picture and the hydnophora, slimer and bit of the green cap in the second picture. I also have a Monti Palawenensis that has lost most of it's green.

I am planning on changing to either 2 x 250 or 400 watt 20K Radium or XM bulbs on icecap ballasts. I am leaning toward the 400 watt as the PPFD on the 250s is about the same as I have now running my 3 light combo. I am also noticing that quite a few of the people running 250 watt bulbs seem to have a bunch of supplemental actinic running. I would stick with the VHO, just when the new lights were off. My canopy is 13 inches tall and has two 4.5 inch fans, one blowing in, and the other pulling out. The bulbs are 8 inches over the water. I can install 2 more fans on each end if needed. I also have a 1/5 hp Arctica chiller. The PPFD put out by the 400's seems to be in line with some of the 250 watt 10k numbers, so I wasn't thinking it would be a problem for the corals to acclimate. My biggest concern is the heat being generated by the 400 watt bulbs. I converted the rest of my house to fluorescent, so that helps with the power bill. Any ideas or advise?

Thanks, Scott