How many plants u growin? i'd go with the 400 if ur doin more than say 2 plants.... but then again, i'm usin a 400 from htg for just 1, but i do got a lil more space than u lol.... Seriously though, The 400 would effectivley light a 3x3 area, which is a bit more than ur workin with. Aside from that, the 400 will put out a bit more heat then the 250.... so temps could become an issue there. What are u plannin on doin for exhaust, cooling and whatnot?