With a grow room that big, I wouldn't suggest florescent lighting. It will not be efficient enough. I would go with either a combination of a 1000W MH (Metal Halide) for the veg cycle, and 1000W HPS (High Pressure Sodium) for flowering. Or if you have a budget, you can skip the MH light and just use the HPS.
MH will provide the "best" spectrum of lighting for your vegetative lighting, but an HPS will work in its stead. HPS is the only light you will want to be using during the flowering stage as buds need closer to the red spectrum of light than the blue to be thick and dense.