couple ways to go about it. It is easier to control heat if you mount the bulb horizontal, make a reflector and use glass. You can get higher yield hanging the bulb vertical and maybe make a cool tube. You could use a 70w or a 150w HPS. Temps may be hard to control with the 150. I built mine with a 70w security light.
with the vertical you would do a V-SCROG, for increased canopy area. I've attached a rendering I did for someone else. Keep in mind it was thrown together in like 5 minutes. Things are not to scale. one shows the horizontal configuration, with intake in the rear. You can also have the intake on the bottom with a false floor for the light trap. It takes up vertical space though.
Install your components in the gutted power supply. You can also install a carbon scrubber in there. With one of those cool fan controllers that mount int he drive bay, you can keep an eye on temps. Soil is the easiest, but I've had good luck with a shallow water culture. If your crafty, you might even be able to do a recirculating system and still keep it stealth.
http://i.invalid.com/wT7Va.jpg
