What caliber is best suited for Buffalo Hunting?

I was recently told I'm going on a hunting trip with some family, I've hunted many deer, elk and coyotes, along with plenty of small game, but never anything like Buffalo. So I'm asking what caliber should I bring? I've looked into this and I see alot about Shilo Sharps and other muzzleloaders but I dont think we're going for the 1800's feel with this hunt. What modern day calibers or affordable easy to get calibers do you feel are best suited for taking a buffalo? 30-06? 30-30?