Dear Mr. Sturmgeschutz,
I advise my clients to bring a 338 Win. Mag. as their working rifle and a 416 Rem. Mag./Rigby/Weatherby. Any of the 3 will do the job on any of the big nasties without a problem and are quite a bit more effective than the 375 H&H.
I think the 416's are more versitile than the 458's. My choice would be the 416 Remmy.
If you have time, have a look at my web site and see what the 416's can do. The majority of the dangerous game there was taken with one of the 416's.
www.go-on-safari.com
Best,
Phil