You are missing the point.. A factory housing can not be aimed correctly with an HID. The light is still going all over the place when you put that much output into the stock housing. You can aim them down but that only helps so much. :;
WT is right... ever notice how a car with factory HID's has a very sharp cutoff if you park the car against a wall and turn the lights on? That's so the HID's don't blind oncoming cars. You don't get that cutoff with standard light housings designed for regular bulbs, so no matter how you aim them, you're still blinding oncoming cars.
And the "HID" bulbs you get at autozone or wherever are just regular bulbs (maybe higher wattage) with a blue tint on them.