I love these little things. So easy to make and mod. I'm running this one at 12V/2A with 3156 bulb. By itself, it's very quiet. With a preamp, it will wake the neighbors. Check out the vid below.
The case is plastic. There is a huge heat sink on the mosfet. If you used a metal case, you can get away with using it to disperse heat, or at least some of it. I made a few in metal boxes and what I did was use a smaller heat sink attached to the side.