sunlight eventually begins to break down the plastic used in the headlight lenses. originally they have a UV coating on them, but once that's gone the plastic begins to degrade. you can buff the lenses up again to get them back about 90%, but you'll find it requires you to maintain them about once a month to keep them clear. personally, i say replace them. they're not that expensive from RockAuto, and are pretty easy to change. when i worked in an auto parts store i'd often have customers complaining about how their headlights were dim and asking whether replacing the stock bulbs with brighter/more expensive bulbs would correct their problem. once the lenses become cloudy the light becomes defused. so no, brighter bulbs will not help. one guy wanted his money back because the $60 bulbs didn't help. i looked outside and saw the most clouded lenses i'd ever seen. they were on a Mopar and looked like they were painted white. worst lenses i ever saw. unless you're planning on replacing your lenses, don't waste you money on better bulbs.