Seriously - really, really seriously - we went up to Dubbo a couple of weekends ago and started the trip at early night on a narrow country road. Being acutely aware that I wasn't revving my engine a great deal and that I was pumping something like 60A down to the caravan, I decided to play with the lighting up front to reduce the alternator load.
With normal headlights only, you can't see squat. It's downright dangerous, and with a 2.5T caravan winding up country hills at night it was ridiculous.
With ALL the lights on it was daylight - and returning to low beam when an oncoming car was seen required half a second for your eyes to adjust to the semi darkness.
With just my front light bar -
one of these - the amount of light was still staggering, there was more than enough depth to the light, the spread was fantastic and there was little that you couldn't see. Adding the roof lights (80W) and a pair of driving lights (200W) was not needed. I'm leaving them there, of course, but the single 120W light bar did more than enough for me to see very, very clearly.