i think the 400 is all you need for that space,save the t5s for vegging,like i said i used 3 t5s for side lighting on 4 plants at a 162 watts,and i never used any for sidelighting on the other 4 plants all under a 600,all 8 produced the same,i just feel that they recieved enough light that the sidelighting was not worth the 162 watts.im not a big fan of sidelighting when useing hps,maybe on cfl grows or useing strait t5s.plus they got in the way of the fan.when people say they dont use much energy,they use 54 watts per bulb on the 4 footers.i do not think watt for watt that they are as efficient as an hps for flowering.they work great when height space and heat are an issue,but im actually takeing them out of vegging right now because i need the heat of an hps because to run heat and lights is not efficient,its to bad becase they produce nice healthy plants.but if you feel your plants need more light then by all means add the t5s,mine were getting what they needed just with the 600.