pps i just thought.. you didnt say how big/small your grow space is going to be... well if you do get a 400hps.. i would have it in no smaller then say a 3x3 space.. coz they do give off quite some heat... so size of light compared to size of room will determine what kind of ventilation you should use.. i.e if you had a 400watt in a small box say2x2 then you will probly have heat problems..give us some details if you may of room size you plan to use and what not.. then we can help you sort out any bumps you may have.. there is nothin worse then starting a project only to fuck up real quick coz you didnt sort out your ps n qs..