Earlier quoted context omitted.
Man, 256 lumens ought to be enough for anybody.
I had a DiNotte 200L (200 Lumens) and it barely cut it. I mean, the optics might have something to do with it... throwing photon from hither to yon without a really good focused area on the road. I'd outrun my light (going too fast to stop in time for a hazard exposed by my light) at maybe 12 MPH on a clear night on the dark backroads. I can see maybe 500-600 lumens being sufficient, but 256 doesn't seem like enough…
You want to focus almost all of the light at the horizon, with some spill below and a sharp cutoff above. Anything else is wasted. See: http://peterwhitecycles.com/plight.asp