A .30 caliber anything is about as versatile as it gets. A 30-06 or .300 Winchester Magnum, or even the new .300 Winchester Short Magnum would probably all make good options. As far as grizzly bears, my Sierra reloading manual recommends something a little heavier, but people do use them for that. Winchester is coming out with a .325WSM, but I don't know much about it other than it shoots a bigger bullet. It might be a better choice for grizzly. As far as overkill is concerned, in my book, if you can shoot it well use it.