i use a wiring harness which makes a HUGE difference getting all the power from the battery to the bulb. this should be one of your first lighting upgrades.
a higher watt bulb puts out more light
but ofter fail faster because of heat & vibration.
i like this rouhg service bulb w/ a harness on the dr
daniel stern recomended it!
jeff @ procycle has some nice inexpensive brackets for optional driving lights http://www.procycle.us/bikepages/dr650.html#electrical
deka (eastern penn, a us company) makes aweseome sealed agm batterys.
this place sells it for less
bike doesn't drag when startign w/ this battery and agm technology is robust.
tpi does sell upgraded battery cables for a cure to slugish cranking, but they are pricey and this battery takes care of it anyway.