hi lofty,the 250w hps will do just fine,used one myself for a year or so many moon's ago!!!keep it at least 50cm(18") away as these lamps give off a lot of heat!!!also make sure you've got enough ventilation in your growroom or you can end up cooking them done that myself when i first started only had a 50mm(2")vent hole,changed from a 75w hps to a 250w hps,hung the 250w went to work come home to find the lot fryed,the thermostat read 135 degree's how the place did'nt go up in smoke i don't know..hope this helps..love an respect..spliffbuilder.