Ok, Yes then. But it depends on how long you are going to keep them in veg, and how many you have, how long from seed you call veg, temperature, ect.
I would say that by the end of the 4th week from seed, you you should be looking at what plants you want to keep. Then look for more watts period. After four weeks, 400 watts over a 4×8 table covered with four week old plants, are going to do nothing but stretch, even with evenly spaced lights.
I have 12 plants now, in 2 gallon pots. To the maximun outside diameter of my pots is 26"×50". I cant move the pots farther apart. They are 45 days old today. Today is day 13 of my flowering stage. One is showing female like she is a week ahead or the others. The other 11 are showing true, white pistils, so I now know they are all female. I am running one 400 watt and two 150 watt lights for a total of 700 watts. I also ran a 1000 watt Highgrow LED along side for the three males that showed before the females. They are gone now after relocating them after I decided which ones to keep and before they opened pollen sacks. (Note that the claimed 1000 watt LED fixture only draws an actual 200 wats of power acording to my Kill A Watt wall meter.)
So, that is a total of 900 actual watts in a 26"x50" space. They are 45 days old now, they are two weeks into flowering and I am probably going to put in a single 1000 watt soon.
I am saying all of this for comparrison. It mainly depends on how many, how crowded they are, and how long you plan on keeping them in veg. I will say you will need more serious power if you want real production out of that size space. Even for veg.
But they will live......