If it was me I would keep the 9.3x74 for plains game that's its Forte ,its about faith and having confidence in the gun you are using ,you don't want doubts,if you do, things are more likely to go to crap .You can get a relatively cheap CZ ,Mark X in 458 Win Mag, make up your own loads with premium projectiles and you have something you have confidence in, and know is adequate ,and doesn't kick like hell ,its about responsibility too ,if the buffalo bolts after being hit the PH then has to deal with it , a story a PH told me about a wounded buffalo he had to deal with was not pleasant, after what happened to him and he nearly lost his arm .