The .450/400 properly loaded is 400 gr at 2150 FPS.

I have always considered the .375s and 9.3s good all-rounders for Africa. As such they are great large plains game calibers that can be used on smaller animals as well, and are capable to provide insurance and kill dangerous game, should it make an appearance. In this sense they are plenty 'nuff gun for any animal on land, anywhere in the World.

A lot of PH guides would even prefer that you use a medium bore against DG if it is what you can handle best. They are there with a .458 Lott or similar to back you up if necessary.

If it were me, though, on a dedicated buff hunt, I would go with a .400 up. The 9.3 used competently will fatally wound any animal, but a big bore will be a better stopper IMHO if you want to do it right, yourself, without backup intervention; and have full control of, and satisfaction from, the experience.

Most importantly, enjoy the hunt of a lifetime! All the best.