Lighting my grow

I have a space that is 36 inches deep by 58 inches tall and 20 inches wide. I am thinking of using a 400W hps on a dimmable ballast set down to 250W in a cooltube. Do you think this is too much/not enough light for 2 plants max in a scrog?

does it fit?

The ducting might be a bit of a squeeze and will probably knock about 12 inches off the height I have to work with but I think it will fit.