Not much any of those rounds will do different, some reach further if you NEED really long range capability. Since I try working w/in 400 yds and most shots have typically come in half that distance, I'd be content w/one good small bore.
A new rifle would be for a different purpose - larger game, my preference would be 338 Federal if not after Grizzly, and the 338/06 or 9.3x62 if so.
Adding a mid/medium bore would be how I would 'diversify' if wanting a 2nd rifle (assuming you will hunt game larger than deer/black bear).
