Think of lumens, not watts. Watts are a measure of power. Different types of bulbs are more efficient, so they use fewer watts to produce the same amount of light. Light production is measured in lumens. You really need at least 2000 lumens per sq. ft. striking your canopy; over 4000 is better. A250w bulb puts out around 25,000 lumens, and you've got an area of 2.3 square feet. I think you've probably got some light overkill; you would probably do plenty well with a 150w HPS in that small of an area and have less problems with heat and stress. Your plants aren't getting all of those 25,000 lumens because your light is farther away...but your light is farther away because of the heat. A 150w bulb would produce less lumes, but you could move it a little closer, which would make up the difference.

But, hey, if it's working, don't change it. Your temps sound good. If the plant looks good at this point, I wouldn't mess with the lighting. Focus on the other stuff; ventilation, temps, humidity, nutes, etc. I can't guess how your yield will be, but it sounds like you've done pretty good with your setup so far. Good luck.