Coming from Australia you'd be hard pressed to beat a good 300 grain Woodleigh PP for buffalo. This bullet anywhere between 2450fps and 2680 fps muzzle velocity seems to hit buff really hard.

If you could handle a slightly more curved trajectory you could go up to the 350 grain Woodleigh. This load to my mind really bridges the gap between the 375 and 416's. It expands, penetrates and does everything you could expect of this class of cartridge.

Not sure what distances sable are shot at for me to offer an opinion, but you'd think a good standard bullet would sort sable out quick smart in 375.