It all depends on what your intentions are for the tank, and your budget. There are essentially 4 options with regard to lighting -- 1) NO (normal output) flourescents (which is what you have); 2) VHO (very high output) flourescents; 3) PC (power compact); and 4) metal halide.
NO bulbs are suitable for FOWLR setups, but not for reef setups. The latter three will work on reef or FO setups, will improve the look of the tank cosmetically, and will better promote growth on your live rock. The drawback is that an upgrade to any of these setups will run you $250-400. If you do want to upgrade, check out the Equipment/DIY page and get a read on what people have to say about the various setups. If you have the opportunity to see each of these systems at work at a LFS, that will no doubt help you form your opinion.
If you want to stick with NO flourescent, you should buy a hood that will support at least 2, and ideally 4 bulbs for your size tank. I have jury-rigged a couple of Perfecto reflector strips together to permit 4 20 Watt bulbs of various spectrums. I have two 10,000K, an Actinic, and a 50/50 (all Coralife). Each strip runs on a separate timer with the blue-spectrum bulbs coming on an hour earlier and shutting off an hour later to better simulate dusk/dawn conditions. I have no idea how accurately this works, but it makes me feel clever.
I would check the make of the "throw-in" bulb and toss it if it is generic. Opt instead for brand names.
If I had to do it over again I would have bought the Icecap VHO set-up from the start. I might do that anyway once I can convince my wife that it's worth $300 to overhaul the lighting. Hope this helps.
