Thought I might point out that you are losing a lot of light to the top of your box. When you have no reflector, almost half the light goes up, and while some light will be reflected back down, it won't be significant enough to matter.
I made one out of poster board from wal mart, 25 cents.
I cut out a large circle, and then cut a small quarter sized hole in the middle, and cut a straight line from the outer edge to the middle of the smaller circle.
Then I wrapped it around the wires and taped the cut back together, kinda like a lampshade.
When they are small as they are now, the light has to travel too far, if you make this you get much more light for your money. If you had 100 watts of bulbs set like you do now, you'd be losing almost half of that to the top, not to mention you're paying for it too! Once they're bigger it will not be as necessary, as you will be bringing the lights closer to the top, but it does help for now, while your lights are not close to the top. CFL's will not get hot enough to ignite the poster board either. Alternatively you could use cardboard and line it with some mylar.
Hope this helps.