just an idea what do you think?

I am limited on the places to grow since i live in a very urban city. I previously grew in a small room but that fell through, so from that grow i still have a 400 watt MH and an air cooled 1000 watt HPS. I want to create a cabinent that is about 3 feet high, 2 feet wide and about 30 inches deep. What do you guys think? is this too much light for a couple small plants?

If the three foot height is total height, then you would need to add add 10" for the 3 gallon pot, 6" or so for the light fixture, 12" for distance from 400w lamp to top of plants. You could conceiveably grow plants up to 6" tall. Heat would likely be an issue, too.

you could find plans for a good box by googling the dimensions.