Can't see needin' anything more than 1x/100 yds. for anything larger than varmints.
I can make 1X/100 yards work if the scope has fine crosshairs. But I certainly don't think more than 2X/100 is necessary. I've under 1MOA at 600 yards with a fixed 6X SWFA scope before.
For 600 yards something with 9X or 10X on the upper end should be fine.