In terms of the current these lights draw, this post might be helpful ....
http://www.pedelecs.co.uk/forum/electric-bicycles/12614-brightest-possible-front-light-6.html#post175868
As you can see, on 'high', the 3-CREE coupled with an MJ-818 draws 2.5A after a 36V-9V DC-DC converter and 0.6A...