Hey rusted, I just started a grow, i'm planning on flowering 4 plants to a height of 2.5-3ft with a 250 watt hps. I figure each plant will use 1 square foot so 4 square feet in total thats just over 60 watts per square foot. I'm pretty sure that will be enough for some good results, so I think a 250 will be good for you.

Good luck!