Have you considered HIR lamps (Halogen Infrared)? They're a relatively new type of halogen that produce about 50% more light per watt than regular halogens, and they have a good hour rating. I used some 9006 HIR replacements in an Acura Integra for about 6 years before I sold the car. I think they were the same wattage as stock (55W?), but quite a bit brighter. I don't know if you'll be able to find some that are lower wattage than stock.
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