you'll have to let me know how the bigbud does, i've been looking into that strain for a while now, I heard it was a good yielder, but only moderately potent. ok, so this might be a bit more managable, because if your planning on using the cabinet for veg and bloom your gonna need 2 lights anyways... a 400w'er could probably do 5 ft comfortably, you split that down the middle, and th light is only having to fill 2.5 ft each direction... also, that would make your bloom area about 5 sq ft, so you'll be pushing 80w per sq ft! that's damn good man!!! you might want to look into modifying your reflector hood (if its a verticle hood) to abou a half hood, so about 2/3's the bulb is sticking into your cab. if you don't have a verticle hood go ahead and just stick it on inside of there, as close to dead center as possible. so to recap, go w/ a 5ft bloom, and a 3ft veg room, the light only has to spread 2.5ft and 1.5ft. I would still get 2 400w'ers only because you want the node spacing to be as tight as possible, so tight noded mothers is a good place to start!