not many places around here stock the 893 bulbs on the shelf. i know theres some others that will fit, but i cant remember off the top of my head. for some reason the numbers 891, and 899 come to mind, but i have no idea if im anywhere near correct.
kinda hard to stick with the 893's if no one sells them around here...Just stick with the 893 stock wattage. If you go any higher with the other bulbs, yes you might get more light output but at the cost of strain on your electrical system, and run the risk of melting your housing.