From all thats been popular lately, i think the answer would be 1x 600w light. Personal pref though, get a digital ballast 400w with hortilux, etc hps bulb that lets blue out too and put cfls too(150w+ output in 27 and 6k, one each?). My friend has his 600w digital outside his room and it makes WAY less temp than the old 400w one. Also, it is SO worth it for a switching ballast, so you can use mh or hps bulbs. I am a floro person for veg personally. What it comes down to: Is this your only area for cultivation? If so, find a switching digital 600w ballast if you plan to go from veg to bloom in one area. Otherwise, a 2/4 foot t5 for veg of mothers/clones and a 400w digi with hps for fruiting plus a few 3 and 6.5 cfls even spaced with sog/scrog is great for your size from what I have seen.