Two good reads here:
http://www.ducatisportingclub.com/showthread.php?t=9951 and
http://www.ducatisportingclub.com/showthread.php?t=9758 I went for the Osram Silverstar and was much impressed but then my headlamp was just plain mucky inside as well.
Dereks idea of running seperate power cables direct from the battery is interesting.
Good luck - Frank