probably cheapest and most versatile light would be to just get a 10gallon incandescent strip light, and stick some daylight CFLs in there
I think something like 2 13 watts is in the upper end of low light, but if you want to go higher tech, you could stick larger bulbs in there ( I think 23 watt CFL are commonly available, and if you poke around, you can probably find even bigger ones.)