Looking forward to your progress as I have a 75 gallon myself that I am planning to start in the near future. How will you place the light - suspended? on legs? right on top of the tank?
According to Hoppy's lighting tables (http://www.plantedtank.net/forums/li...t5-t12-pc.html
), 4x54w T5HO can be too much lighting for a 75 with respect to how it is placed. I thought about getting a 4-bulb fixture too, but am not sure yet.