I cant tell you what exactly you need but anyone on here who can will need to know exactly what kind of setup you have and what you plan to keep?
Some base it on watts per gallon and others take it on a case by case basis depending on the depth of the tank and so on...
There are three types of lighting you can use
Power Compacts
VHO : very high output
Metal Halide
it all depends on your setup I believe, just post your tank size and dimensions what all you have and what all you want to keep and they will let you know!!