I would try some 225 broadheads first, before I made any decision. You really find out how well tuned your arrows are when you put the broadhead on for the first time.
Also, if you go with the 100gr. insert and it is longer than the the insert you are shooting with, with your field tips, it will make a difference. I know I have some 100gr insert and them suckers are long.
So what I am trying to say is, by changing your insert, and not testing your arrow flight with a broadhead, the combination of the two could throw you out of wack.