Paul,

The power of the bulb is a small part of the effectiveness of the headlight. The 124 US headlights have extremely poor reflectors and lenses. By adding a brighter bulb, you will gain little in the way of lighting effectiveness. What you WILL gain is an overheated light fixture.

I am facing the same problem and plan to put in European headlights, this is the only real way to fix your problem.

Good luck,