My experience with it is from the early 80's. I've shot a number of animals with it and never saw all the problems everybody wanting a new rifle see. I notice that Hornady has a 500 grain bullet at 2250 (advertised). If it is true their is nothing it won't do.

As to a Double Rifle in 458WM, that is different. What is the loading that you have to use? That will tell you if you have a DG Rifle or a souped up 45-70. I also do not trust rimless cartridges, especially not in a DG Rifle.

What kind do you have? You know that if you like the rifle you can get it rechambered for very little to a 450 3.25 or a 450#2. Both of them are the equal to the 470.

There is no need to take the 458SxS and the 470. Neither is a particularly good choice for plainsgame. A 375 could do double duty for the Buff and is a pretty decent plainsgame rifle also.

I think if it was me, and I liked the 458, I would rechamber it and skip the 470. Use the money for 5 more Cape Buffalo.