I agree with eslm. If you have the room and the cash, sure an HID will give you the best results... BUT, if you have limited space and funds, you can get high output CFL's that are very satisfactory. I've used a 250W (actual) 6400K for veg. and the same bulb in a 2700K (red spectrum) for flowering on my last two attempts, and was quite happy. I kept around 5" of space above the plants at all times. I have a space of 18"W x 24"L x 36"H, so I get plenty of light with little heat and a low electrical bill.