OMG
1. The 7x57 will easily move a 175 at 2600.
2. There is a lot of misinformation about muzzle energy and cartridge minimums in Namibia. The game ranches own the game and manage it. You can use darn near anything if you can shoot well.
3. A 375 will work if shot well but that amount of power is not needed if one can shoot well.
