I'd stay away from a 6.5x68 unless you want to shoot it very little or replace the barrel in 900 to 1,100 rounds. The case capacity is about the same as a .264Win Mag, which makes it slightly hard on barrels, except due to the short neck and sloping shoulder, is a bit harder on throats than the .264 WM.

The 7x47 Mauser from a 24" FN M98 will make 2,960fps with 140gr., 2,800fps with 160's and there is no need for anything heavier - just pick your bullets wisely. As to range, it will handle any game suitable for the bullets chosen, at whatever range you have the capability to accurately make the shot.

I'd go for another 7x57Mauser in a heart beat, given the choices you present.