Look around some sites and youll find that 400 watt lights are only a few dollars more expensive than 250 watts. you will be better off to use a mh before hps, its the right spectrum for vigorous growth in the veg stage. Hps is better for flowering because it will cause your plants to have high yields, but many people will tell you that using a mh for the last few weeks of flower will increase the potency of your marijuana. its really personal preference, if your using a 250 watt light im guessing you could use cfls for your setup, that would be best for bushy plants with nice thick stems. cfls reduce internode length and are generally safer to use because your plants have to touch them to actually be burned. HiDs on the other hand will always make your plants a little more leggy, due to the fact that the light source is so far away, and burning plants is a common mishap.