It looks like you came to your senses in time, so I will try to keep this as short as possible.

The .375 H&H is all you need - period. With a good 300-grain solid at 2 500 ft/sec MV it will shoot straight through the skull of the biggest bull elephant and whistle off into the distance. I know this for a fact, I witnessed it first-hand. With the same load, shoot the biggest bull buffalo in the chest and you will recover the solid in his arse. I know, I have done it.

You want to shoot softs? Load a 300-grain Swift A-Frame for the heavier stuff or Woodleigh Weldcore for the softer stuff to the same MV and just shoot them. They will fall down as if struck by lightning if you do your thing.

The .375 Weatherby makes more noise and delivers more recoil, and does so with significantly higher pressure as well. It has a bit of a nasty reputation over here for failure to extract due to higher pressure, so it is pretty low on my personal list so far as DG rounds go.

The .470 Capstick I have no experience with but it is by all accounts a very effective round. But rebarrel/rebore a perfectly good .375 H&H for one ????!!!! Over my cold, dead body!

Stick with the .375 H&H. In three months's time you will be glad you did.