The H4 relay kits from Eastern Beaver <
www.easternbeaver.com> produce noticeably brighter lighting with standard bulbs and can be used safely with higher wattage bulbs providing the reflector and headlamp housing can stand the extra heat.
Before I installed the H4 kit I measured the voltage drop from battery to headlamp and found it to be about 0.9 Volts on low beam and 1.0 volt on high beam.
Afterwards, the same measurements yielded 0.09 volts drop on low and 0.1 volts on high. Looking at the power equation where Power = volts times amps you can see that the power level has increased about 5 Watts on either low or high beam. The difference is noticeable to me AND anyone riding ahead of me, day or night. The bulbs are now at about their rated level of 55W/60W low/high instead of about 50/55 without the relays.
I suspect the lumen level has gone up even higher, but I don't have anyway to measure it. The color seems whiter, and the low beam cut-off seems better illuminated right out to the edge -- no "holes" in the light pattern compared to the level without the relays.