Outfitting my cyclocross bike to start commuting to work. AM commute is in the dark and a couple miles on pitch black untraveled roads (part is dirt). I am trying to choose a headlight setup. I am looking at a 400 lumen Niterider system....it's kind of expensive, but the 200 lumen version is cheaper. How much do I need???, I have no reference for what brightness is required. Thanks!