no the 6 hours is for you not the plants, like to save electricity or to bring down the heat if you have H.I.D lighting.
metal halide bulbs if thats what your talking about do need a special ballast and socket so maybe the cfls would be your best bet especially for a closet, the mh's get very hot.
There are probably tutorials for what your looking for with the light set up either here or some other similar site, but I would just drill holes in the top big enough for the cord and plug to go through then you can adjust the height individually if you have to and then just get a power cord with a bunch of slots, they make them with like 10 or more plug ins and cfls dont take much power so you can put them all on one line. hope this helps a bit