mate, for a grow room that size, I wouldnt waste my time with going to home depot (im english I have no idea what that is!) or B&Q, or Wal-Mart or ASDA, searching for the little 40w CFLs you get, because they will be USELESS if your rooms 4ftx5ftx7ft, you'd need like 100 bulbs to get anything! Get on eBay, and go straight into the 125/200/250watt CFLs, they cost around £20/bulb but are well worth it! One 125watt CFL is equal to over 600watt Incandescent! Mines been running for 24 hours and I can still hold the bulb with my hand (Tiny Tiny amount of heat). I would personaly use at least 4x125w bulbs for a room that size, blus extras for under canopy lighting. My tent is 60cmx60cmx140cm-tall(2ftx2ftx4.5ft) and im using just under 400w for vegitation, and 750w for flowering. To make sure I get the absolute BEST my plant has to offer. Otherwise, whats the point? You wouldnt raise your child to be only half of what they could be. I know people will say HPS and MH are the best for my plant, well yes they are, but theyre not for me when the old bill come storming through my door because my rooms letting out more heat than Mt Vesuvius destroying Pompeii!! =]