... he has several rifles to choose from for his "Moose battery", but he is thinking about a new optic to go on his Ruger Hawkeye 300 Win. and in his words, suitable, power wise for possible shots from 40 yards to 400 yards.
I'd say he's pretty much just described a rig that will be not only fine for moose but for any hunt in North America.
SPS has 30 caliber 200 grain partitions on sale, for crazy cheap, by the way. I'd say that's about all that's missing from the specs.
I've killed antelope to 400 yards with an M8 4X but if a variable is a must I agree with those who've said no more than 9 or 10 on the top end is fine.
For some reason I rarely see challenged, for a given level of optical quality, a 3x9 is more expensive than a 2x7, and a 4x12 is more expensive than a 3x9. Keeping the "size" to the minimum really needed lets you bump up the optical quality for a lower overall price.
Cheers,
Rex