Hi Jim,
Honestly a 2.5-10, 3-12 or a 3-15 would be a much better choice, and here's why. Lets just say you see this monster buck, the higher magnification you go, the better the optics you're going to need, meaning big bucks, and I don't mean deer, but here's the real kicker. High magnification will make those cross hairs move that much more, and as you watch them dance around your buck of a life time to the point of you holding off from pulling the trigger, he will be that much further into Canada! Ok, lets say you do hit him. Upon walking up to the downed animal you think is dead? Only when you poke him in the eye with your barrel he blinks...... and bolts up with his horns sticking you in the back shoulder, which saved you from having them punch through to your lungs but he's off and running again! Now you'll want that low power for as wide as field of view as possible, and so you wont see those cross hairs bouncing all over creation so you'll pull the trigger! And yes that is a true story because it happened to me in Utah with a Mule deer.
Sound about right? I used to live in Montana myself, I now live in the Panhandle of Idaho, a lot of this forest is so thick I don't even like walking though it! And yet I've seen Elk 2000 yards away using nothing more then a 3-12x50 or a 3-15x50. This is the same spot where I can drive to for shooting at the steel that I have put up for target practice behind my house. I have never been hindered by the 3.5-10x40 M3 Mark 4 I use on my 6.5/300 WSM out to 1200 yards to ever think I'm outclassed in glass. My Jarrett 280 AI wears a VM/V 5-15x42 Zeiss, but that's only because back in that day they couldn't make a 5x zoom, but it was a dedicated long range hunting tool so that's what I bought and it was light weight which I needed for a hunting rig.
The US military has recently bought a huge shipment of Schmidt & Bender 5-25x56 for their 338 LM's, but that's a special purpose rifle, for 30 plus years its been a 10x40! About the only thing I could say for using more magnification on a rifle is precision rifle shooting, but that's for shooting targets, from a fixed position, not game animals that can be 10 feet away running or 600 yards away feeding.
Keep it simple, and buy something for its intended purpose. More is not always better, as much as men seem to think so, most woman would rather have there guy know how to use there equipment! Which works in the bedroom and in field craft, so don't get caught up in more is better.
It's like the saying "use enough gun", which people took as use more because of the law of large numbers, sure, but if you can't hit it what does it matter?
