All the big game you listed have been successfuly hunted with the 30-06 for well over a hundred years. This would mean that the 300 WSM would work equally well as would the 300 WM or Weatherby version. If recoil was no issue, I would buy a 300 Win Mag and never need any other rifle for big game. With decent hunting skills and shooting skills, the rifles grom 260 on up will all handle those hunting chores. If I were hunting mostly Grizzly and or Brown and Polar bears I opt for the 375 or 416 Rem or Rigby. I would hunt anything with the 300 Mag as I would the 338 because having used both, I can't see any advantage of the 338 overthe 300's. The 375 is another story though, thats a step up big time.

Use your 300 WSM with a good 180-200 grain bullet like the Nosler Partitions and you will never need anything else.