Well, going from 8-CFL to a 150W HPS, the new heat was staggering. I doub't 250 will be much more. a 250 will flower in 2x2 very well. With a fan blowing directly towards the light, i keep it right on top, <2", to perfectly cover ~1.5X1.5X2.5. It is not air cooled.
Your intake temps and CFM...