Grow Dresser Project Help (Pics Coming Tomorrow)

I have purchased a dresser with five shelves as the starting form of my soon to be grow box. The Dimensions are 42" Tall Grow Space (Including where I have to hang the lights from) by 39" Wide by 19" Deep.

I'm going to run a 400 Watt MH for Veg and then Switch it out with a 400 HPS for Flowering.I was just on: http://www.uk420.com/growroomtools2.php and it rated my (hopefully) future light setup at 7,800 Lumens per Sq. Ft, is this enough to grow four to six plants from maybe 2 weeks to flowering, as I already have another area set up for vegging, with 3 23w cfl's 6500k and 2 23w 2700k feeding my seedlings, and i currently have one 2 day old plant and two one day old plants.

The reason I said foru to six plants because my grow dresser can hold up to eight of my final resting pots for my pot, and with a 400W I should be able to grow a quarter pound to a half pound every two or three months, right? That is only a half per plant or an ounce per plant, that's not pushing it is it? If it is, how much do you guys think I'll be able to grow then? I will ScroG if needed.

I am growing in soil, but am very curious about DWC, anybody experienced enough to teach me?

lets see here.. first most important advice.. .. the difficulties ive had is often moving air and keeping it light sealed.. im always trying to rig up my up my own fan contraptions works decent somteimes there noisy.. basically unless ur climate is really cold if u have a good amount of light in there.. it should need venting... if u have a closet where its not hot at all ... and maybe ur hps bulb is about 3 or 4 feet away... it should still be warm in there with a 400... warm enough that it should have venting.. also plants like a ton of fresh air.. there not gonna be super happy in a closer that donsnt have fans recycling the air..go easy on the nutrients.. its worst to burn ur plants then starve them a little... go out slow on nutes.. get a ph kit and learn to ph.. i just ph'd for the first time tonight actually. kind of a bitch to get it hopefully right enough but im glad i gave it a shot and hopefully ill see speedyer growth now that ive added quite a bit of ph down...which is acid.. guy at the hydro stores guess was right.. i needed ph down and prob wont need ph up