Another vote pretty much along with what Aussie said: Any good bolt-action .30-06 loaded with premium 180's will do the job if you do yours.
Some people prefer more power, and I have used the .300 and .338 Winchester Magnums, the 9.3x62 and .375 H&H on various safaris. They all kill plains game too when pointed right, but the .30-06 works fine, if you do your job.
A 1.5-6x, 2-7x or fixed 4x is a good choice for the scope. Even the all-American 3-9x is more than needed, and something a little smaller bypassed any chance of the scope being cranked up too high.
