full spectrum is best dude.. at your roomsize (16+ square feet) and if you want the optimal 50w per square foot (16*50=800w) two lamps would be perfect.
On the other hand, you could save energy/money if you could trade in the 4 400w lamps for 2 800w/1000w lamps and get a light mover, this would allow you to cover a large area with a single lamp. During the flowering phase especially, a larger wattage lamp will give more bud, which is what everyone wants