many here use CFL very successfully but here is my recommendation for a low cost LED bulb that will work in a small cab...it is only $42! :thumbsup:

High Power Hydroponic PAR38 42 LED Grow Light 85 - 260V - eBay (item 220568901137 end time Mar-12-10 02:06:05 PST)

your plants will be much happier with a good LED spectrum here is a picture of a friends plants in a 2'x3' space vegged for 6 weeks in 1 gal containers using 2 bulbs with a total of 25 watts!