Well the first step is to go HERE
and input the dimensions of your tank. While there is still some controversy out there about what constitutes medium/high high light, this site really has been reseached well and it seems to be more reliable than just watts per gallon for the light levels.
Next, you need to decide what type of lighting you want to have. Compact Flourescent lighting will provide the moist wattage and lumens for the size of the fixture. T5 would be next with T8 then T10. Each one of them requiring more and more bulbs to reach the light levels you want.
If you are into DIY, then it could be really easy to get a light for your tank through HERE
. By getting the reflector and the right retorift kit you could easily reach the lighting you need for the levels you want.
One note on the amazon sword. Once you go to much higher lighting the sword could very easily overtake your tank and become more a neusance than a centerpiece. I grew one to well over 16 inches across with just barely over 3 w/g of normal flourescent lighting in a 10 gallon tank.
(Post moved to freshwater plants, should get more help and more useful information there.)