Im just not convinced the magnums offer any more power per say.
This data here shows different calibers, different bullets and the results, in expanded diameters and depth of penetration. the 30-06 holds it own with even a .338 and actually does better than the .300. with certain bullets. One of the 06 bullets show .8 diameter expansion, thats a big hole.
the 8mm magnum shows huge expansion and deep penetration
http://www.rathcoombe.net/sci-tech/ballistics/methods.html
Z, I understand what you are saying, but within the boundries of "one gun" and "ALL N.A. game" I don't think I could bet my life on anything less than a big bore or .30+ magnum for a big, angry bear! They can take a licking and keep on ticking!
I think the best bet would be at least two guns. Smaller caliber for most game and a big one for hunting big game, or hunting where big stuff lives! If a person is not going to be actually hunting dangerous game, I'd prefer a smaller caliber for hunting and at least a .44 sidearm for protection!
Either way you slice it, it's two guns or one BIG gun!