I 2nd that. I use 100w basking bulbs with my chams and the light is about 10 inches above the highest basking point and the warmest spots stay pretty consistant in the high 80's. 250w is serious overkill though. Your temps will be out the roof.
75 watt for me as well using a deep dome lamp placed directly on top of the cage. his basking spot is about 10 inches away from the lamp letting him get to 90-95 degrees when he is basking. 250 is considered high even for bearded dragons which can cause brain damage as well as burns.