I did my first plains game safari with a 7mm mag. Took everything from springbok to kudu without a problem. My hunting pard had the same with the same results. Your 7mm wsm will do the job with 160 Nosler Partitions or TSX's.
Don't buy another rifle, use that money for more trophy fees!!!!
Not an African hunter. But, taking the gun you can deliver with and close the deal with is the way to go. My experience with the .338WM and .340 Wby, to me they kicked too much. Both of mine went down the road.
Check out JG'g 7RM experience using 160 NAB's. NPT's or TSX/TTSX's would probably work as well. His rifle liked NAB's best. Partitions are his personal favorite, generally.
http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/8867802/1DF
