Hey ar333,
I am still a newbie myself, so I wont give any input. But what I can say is, there is a lot of info on RIU, so do yourself a favour, and go read the sticky and guides in the newbie area. You will learn alot. There is basic guide, soil guides, light guides, even guide guides. After spending some time reading up, I am sure the experts wont mind assisting with the info that u have missed.
As for a pc grow, I cant see that 400watts is a necessity, but the more light the better. I remember reading something along the lines of 100w per plant, and an extra 50 for every other?
Secondly, ventilation is gonna be key in a pc grow because its gonna get real hot, real fast.
Good luck, and read read read.
PS, u can edit posts