Have the Kimber chambered in 105 mm Howitzer. That way you will never be "undergunned."

Of course, I'm being facetious. I think your choice needs to be conditioned on what game you intend the rifle to be used to hunt. If you want to use it to hunt everything, .30-06 comes to mind. If you want to use it for white tail deer, mule deer, and pronghorn antelope, .25-06 strikes me as a better choice. For bigger animals, bigger cartridge, though I'm not clear what animal the .25-06 would be "not enough gun" and the .270 would be "enough gun" to hunt. I would want more than the .270 for elk and maybe also mountain goat while I think the .25-06 is probably enough for sheep.