Best Way to SOG in 4x4x7 ft tent - What more do I need then I have?

Hey guys, have 4x4x7 ft. tent, and am planning on doing SOG with 12 in that space. I am getting a 400w HPS but was debating between 600w. That's for the flower but what should I use for the veg stage?

Also, how should I arrange my tent or make it so the lighting doesn't interfere with the other stages. Any input would be appreciated, thanks!