I would like to hunt Africa within the next two years. I want to do it with a double rifle. I have multiple bolt guns that include a 9.3x62mm, several .375 H&H's, a Ruger Magnum .416 Rigby, and a custom .458 Lott that is built on a Remington P-17 Enfield action with a Douglas barrel and a handy Ruger Number 1 in .450/400 3" Nitro Express. I just plain want a double and I have honestly never hunted with one. My question concerns caliber. I have my heart set on a .500 Nitro, but am having second thoughts due to that caliber not at all being versatile. I don't want a .450 Nitro as that would be redundant with the Lott, as would the .470 Nitro Express. I am asking for input concerning a .450/400 3" double or a .500 Nitro double. A .450/400 3" might be very light and handy and certainly more versatile. I only want to shoot a cape buffalo and maybe a hippo and I know that Taylor loved the .450/400 Nitro as did Karamojo Bell and many others. After all the .404 Jeff was about right for elephant cropping. With the cost of the hunt being so expensive for me, I want to only buy one double rifle and I want to make sure I am buying the rifle that best suits the mission. I understand that I do not need it as I have many rifles that can do the job with certainty, but my dream has always included using a double and I want to fulfill my dream. I appealing to any of you that have experience in Africa with doubles. I want to make an informed purchase. Again, I will only be hunting cape buffalo and maybe a hippo. I don't want to hunt plains game, cats, or anything like that. Any and all input from experienced double users would be greatly appreciated.

Thank you in advance.