I just went through a similar scenario for a twenty gallon long. Your tank is about 36 inches across, am I right? You want something that will span the entire distance and be in the 6500K range (for the plants). I went with a T5 setup. Try this;
Odyssea T5 Aquarium Lighting
One thing you should do no matter what you decide on is set everything up and monitor the temperature without any animals in the setup to make sure everything is within acceptable ranges. I had the foresight to do this and learned that I only needed half of my fixtures lights turned on tomaintain adequate lighting. My temp went up too much with all of the lights on,but that may have more to do with the dimensions of my tank. I only have about8 – 9 inches from floor to ceiling in my tank, so you probably wont have to worry about that.