hey,
lighting is a very 'subjective' issue... It also has a lot to do with what you are wanting to keep. If you know you arent going to kepe SPS coral or other light needing corals/critters, then you can go with most any type of light, but if you want or think you might want more SPS or more colorful corals then you might want to go with a Metal Halide or High Output flourescent fixture
Personally, I suggest you go with a metal halide fixture... they make them in 70 watt or 150... (150 would be WAY too much for your tank, unless you were to go ALL SPS... You can find them on Craigslist or ebay....
Try to find a fixture called VIPER metal halide
You can find Coralife fixtures also. I see them on Ebay a lot
T5 fixtures are good, but in that size, (less then 24") they will all be NO normal output
the big issue might not be light INTENSITY, but rather light color...
aquarium bulbs, (reef aquarium), tend to like blue colors... vs yello color...
and like a lot of things color is VERY subjective...
So, what i think is blue, some might think is green...
and although there is a NUMBER to define colors, it still comes down to sumbjective...
the number/color range I suggest you try to look at is 14000k - 20oook
colors that are lower/smaller then 14oook are considered more yellow, which will lead to green when it comes to reef tanks
BTW: I know lights are expensive, but i tend to think of them like we used to think of speakers on stereo systems... buy and get the best you can afford... if yo uhad the best/top of the line speakers, then you can upgrade and do all kinds of things with the stereo system...
but, without nice speakers, ...