And yet another way to look at it....
You are hunting impala in big 5 country. You have the privilege of hunting alone and all by yourself. Are you under gunned with your 375, or are you over gunned for impala hunting (Remember that the chips can go down at the drop of a hat...)?

IMHO, carry what makes you feel happy! If you feel happy to shoot an impala with a 500 jeff, then do it! If not, use a smaller caliber, just make sure you trust your PH when the chips are down (or own a good pair of running shoes!)!