The only problem with going hydro is the need to keep the res temps down. It is kind of hard in that small of a space. I used to grow in a 2'x2'x5' area with 400watts and 465cfm exhaust.
I only grew like 4-6 plants at a time, and usually ended up with like 6oz or so. When I upgraded my 2'x2' cab for a 2'x3' cab, I tried 12 smaller plants, and ended up with a smaller yeild by about an oz. I like to have one plant per sq ft. It seems to work out well.