I made my very first light from a security set up from Lowes/HomeDepot. I would never do that again as it was so freaking expensive. I use Econolight.com. They only supply up 400's, a great floro place, but IMHO, you cant beat their prices on kits.
I usually buy like 5 mh kits, and 5 hps kits. I have been using 2 seperate boxes for years now, box 1 has a pair of 150hps's and a 70 mh, for 370 blended watts.
The other box is a 150hps and a 70 mh. I think a kit and a pair of bulbs hps/150's cost $80.00 or so. They are electric supply house not a shop, so it's way safer IMHO.