there are a ton of threads on this topic -- here's a recent one (I searched forum for "h4 led")
https://forums.pelicanparts.com/porsche-911-technical-forum/1109529-h4-led-upgrade.html I've been VERY happy with higher wattage halogen bulbs in my H4 housings -- specifically
http://www.amazon.com/exec/obidos/redirect?link_code=ur2&camp=1789&tag=wwwpelicanpar-20&creative=9325&path=https://www.amazon.com/CEC-Industries-Halogen-Headlight-Bulb/dp/B002CYTQH0 When properly aimed (KEY with h4s), even the standard wattage bulbs should be a clear improvement over our 86' sealed beam headlights. If your bulbs are currently "dim," I'd start by confirming they're properly aimed and that the reflectors/insides of lenses are clean before dropping $ on new bulbs.