Purpose

Being able to see at night (and during poor weather conditions during the day) is very important.

Run, do not walk to the nearest source of Hella motorcycle lamps.  These are two piece lamps - lens/reflector with a separate bulb.  Standard bulb is a 55/65 watt unit.  You can also fine 85/100 watt units that are even better.  The Hella lamp gives a remarkable low beam pattern with a razor-sharp vertical cut-off.  With these low beams you may not need fog lamps at all. The High beams are good enough that you probably won't need much in the way of driving lights, especially with the 85/100 watt bulbs.

Thanks to Bill Taylor for the tip.