The most important element for good headlights is the shape of the reflector and lens. That is why you have Euro lights, they are vastly superior in this area as compared to the crappy US lights.
For this reason, there is absolutely ne need for high wattage bulbs. In fact, if you use them the added heat will eventually do damage to your headlight assemblies. Just go find a standard H4 bulb from Osram, Sylvania or whoever. Buy a spare while you're at it.