I was actually going to have 8 plants, but even so, you think a 400w should suffice? Looking at my drawing there, where would you stick the fans for optimal airflow? I'm trying to keep this setup as economical as possible.
Edit: I have a pH testing kit, so I was thinking of just using a turkey baster to grab some water, and throw into my kit. Either that, or drill a hole at the base of my bottom container, and actually put the entire thing inside of a tray? I'll come up with something to simplify this. It depends how often I need to test the water, and change then nutrients.
Also, given the space that the plants will have to grow, and the the excess space to allow for the roots to grow, how much would you say my design would yield. Close to a pound?