Hi Chris
you need to be very careful increasing the wattage of the headlight globes as this in turn increases the load (Amps) flowing through the headlight circuit. Generally headlights have a 60/55w high/low beam glove and a 60W high beam. Headlights are very good now a days and the really isn't a lot of need to go silly with high wattage gloges. There are new globes out now called +100's Check them out here They have the appearance of a very high wattage globe with out the wattage so the electrical load on you system is not changed.
Hope that is of some use.
Cheers
JR