I'm using a 250w HPS on my 1 plant and might go to 2 plants.... spend some money on a nice light/s and it will pay you back big time. PS: I don't have alot of experience but I have read alot, so don't just take my word for it.
Yea a good one starts at around 150 and they go up from their. www.grow-light.com http://www.marijuana-seeds.net/Lights.htm
Nobody here seems to be aware of industrial lighting distributors...same stuff at a fraction of the cost...grow shops are run by the cops...online purpose built grow lights are a rip...find a wholesaler near you...any town with more than 30,000 people will have at least one...
those lights from inside sun for $90 are good lights .they are old street lamps .i bought a 400 watt mh from them and it's been great and you can buy a better reflecter on ebay for $30...but i'm currently useing the reflecter that came with it and it's working just great...the mh light uses a magnatec ballast which is pretty much silent ...also they come with new bulbs...very good deal with very prompt delivery...there is no minimum order so you can just buy one if thats all you need.
also most of the industrial lighting suppliers..that sell wholesale require a minimum order and some even require a electrical contracters license to make a purchase....