your going to get a Gambit of answers, but imho, yes. I use one 400w CMH in Veg. 4x4 room with 7ft ceiling. im also of the mind, too intense of light on clones stresses them to much.
18/6 on clones and veg with nice growth. Im in a transition point atm, with my rooms, and have created a temporary room to hold veg in until this current round of flower is finished.