you cannot reduce the power. the salt burns at a specific heat and thats it. the gas mixture in the bulb is what determins the colour heat (4000K 6000K 8000K etc) 4000K is white, 6000K is slight tinge of blue and 8000K is blue. its not legal, none of them are but if worst comes to worst you can try to argue it out that as the law stipulates (in QLD anyway) a "self leveling" headlight can have HIDs and since you havea BA with prijector lowbeams your could be classified as legal as the light is allways leveled off at a certain point due to the projector design and minimal light is that can "dazzel" oncoming drivers escapes past this highest point. if you get flashed a few times only thing you can really do is to lower the projection of your beams to face more to the ground. if you removed the headlights to install the HIDs you might have screwed up the height so go to a nice flat wall at night and shine your lights at them, and make sure that your drivers side beam is lower than your passangers, and that your passangers comes out parralell to the gound IE the tallest part of the beam projection on wall is "same" height as the headlight
hope this helps mate
Tony