the top of the range Denali appears to give around 200 meters with the beam still being effective. At approximately 100kph I think that is around 5 seconds reaction time (I am sure someone will chime in if the approximations are out). With some bigger lumen LED lights you may be able to extend the distance out a bit further. From memory the Clearwater ones have a usable distance of around 300 meters, punching the distance out a bit further with HID should add a few more seconds (possibly 8 or 9) onto reaction time.
May I suggest that you may still need to slow down at night to compensate for the loss of vision.
Any extra light that you can put out front is a bonus, the Denali is a good brand as are a number of other LED lights out there, remember that you get what you pay for.
