I bought the factory recommended unit. Cost $34.95. It mounted in a matter of minutes, I tapped into the wiring that was provided specifically for the unit on the tractor. The whole project took 10 minutes from the time I opened the box to the time I hung up my tools.
The light is a bright halogen bulb that is MUCH brighter than the headlights and throws a nice pattern. I do not see the need for 2 lights based on my use and based on how bright the factory light is, also the housing allows for adjustment so you can easily aim the light.
You can probably get buy much cheaper than the $35 unit from the dealer, but if you figure in you tinkering time, it might be cheaper to just use the factory light & mount!?!