As Guy said, heavy arrows and 125 gr heads have been killing things for a LONG time. That doesn't mean we can't do better, tho. We put a lot of effort into getting the most out of our bows, yet many bowhunters are afraid/refuse to look at optimizing their arrow performance as well. The arrow/broadhead package is what does the killing and is far more important than the bow.
Dr. Ashby's research with several thousand well documented impact shots have clearly shown that higher FOC's directly relate to increased penetration performance as long as the arrows are tuned to shoot the heavier front weights. Tuning an arrow to shoot a 200 gr broadhead is the same as tuning to shoot a 125, it just takes a little more spine.
When everything in the shot goes like it's planned, most any reasonable setup will do the trick. It's when something goes a little wrong that the extra really helps. Don't be afraid to try it; you might find you like it. I know I do.