I came across this while doing some research for myself today that should answer your initial question.
You have 403 sq ft total with 16 - 400 watts light you have 6400 total watts.
Smaller plants should have 20 - 30 watts per sq ft. larger plants should have 30 - 40 watts per sq ft. During flowering 40 - 80 watts per.
So at 30 watts per you need = 12090
at 40 watts per you need = 16120
at 80 watts per you need = 32240
So I would have to say you don't have near enough. That is also figuring that the light will be very close to the plants like 4 inches or so. Than again the HO bulbs put out nearly twice as much light as regular fluorescent lights.
Feel free to check me the following is a quote with the info that got me to where we are now. The two links here have a huge wealth of info on indoor lighting. It seems like you know what you are doing but you may want to browse them. I spent several hours reading through all the info.
Good luck, I hope this helps.
What Size Light?
Seedlings and clones, and even small plants in the vegetative stage, will do just fine under 20-30 watts/sq foot. Larger plants in the vegetative stage will do better if given a little more... about 30-40 watts/sq foot. Plants in the flowering stage require a lot more light, and should be given 40-80 watts of light per square foot. Again, these are general guidelines that should work well for plants that enjoy lots of light. It is always a good idea to know the lighting requirements of the particular plants you are growing.
The first step in choosing the size of light you will need is to measure the floor space of your garden area (example: 2 feet by 4 feet= 8 sq feet). Next, multiply this by the watts per square foot you would like (example: 8 sq feet times 50 watts/sq foot= 400 watts). Break out your calculator if you need to, this is important to your indoor gardening success!
In the example above, you would need 400 watts of light to put a 2x4 foot garden at 50 watts/sq foot. As luck would have it, a 400 watt light is one of the standard sizes. The standard grow light sizes are...