How much light will I need?

[Manny]

I have finally finished my stand and got all the plumbing done. Now I need to get the lighting done. My tank is 24"Lx24"Wx25"H. It has an external overflow so none of the tank dimentions are taken up by the overflow.

My question is how much light will I need to keep SPS and some LPS and a few softies. I was thinking that I would use a 400watt DE flourecent combo but I can't seem to find any 400watt, only 250watt. Would a 250watt be enough for a 25" deep tank. I would like to stay with the DE due to heat issues.