I'm sure you can take almost anythign with anything, I heard that weatherby himself took a cape buffalo with a .257 wby, though it was by accident! I beleive the animal or so the story/legend goes dropped on the spot!

Personally I tend to like bigger stuff for bigger stuff. Also you get to use a new/different rifle for the big stuff, what fun is using a .30-06 or .270 on everything? I like a little variety, so I say break out the .300 or .338 mag, hell even the .375 some guys like. 7mm mag will work too, I'd take it over the .257wby for elk thats for sure.