It may not be getting much press lately, but IMHO there's nothing wrong with the .458 Win Mag. (Full disclosure: I have no experience hunting any kind of dangerous game.) I'm currently having a custom .458 Win Mag built. Nothing fancy, just a solid working rifle. I'll probably load it like a "super" .45-70 / .450 Marlin and use it on feral hogs here in Texas. A 350 gr Hornady at around 2200-2300 fps should work great on hogs.
Here's an article from African Hunter magazine that you may enjoy:
What is wrong with the .458?by Charlie Haley
http://www.african-hunter.com/WhatsWrong.htmCheers!
-Bob F.