Re: Magnification needed for 1K to 1 mile?
Quality of glass and repeatable turrets are more important factors than magnification. Just because a scope can go to 25X means nothing. It could have a horrible picture, tiny exit pupil, painful eye relief, etc, so what did you gain by 'going 25X?' A headache after an hour of shooting. 50 year old eyes and neck and back need forgiving eye relief and a good quality optic before considering power settings.
It also of course depends on the kind of shooting you are doing. My buddy with his 22 at 50-200 yards siting on a concrete bench wants more magnification (25x) than I use at 800+ yds. He is under no time pressure. His targets are static, square, well lit, etc.
A fixed 10X can nail torso size targets beyond 1000 if the guy running the trigger does his job.
If this helps, at a shoot last year I kept my 5.5-22 at 11X all day, even out past 800yds . . .
Today I was behind 3 rifles at 1000, and the one with an 8-32 NXS I turned down to around 18x, it was just easier to shoot at that power.
If I can remember tomorrow I will take through the scope pics from 1000 to 2000 with the new NF F1 at 15x. Today it did its job at 1000 yds. The reticle line will be a bit thick on small targets at distance, so it all depends on your target size (ie torso steel or paper size, vs 1 MOA size target).
I think the perfect all around scopes to 1000 are the USO 3.2-17 (GAP reticle) or the NF F1 3.5-15 (MLR2 reticle), but there are certainly other brands that have their fans as well. Take this as one opinion from over 40,000 on this board...
The best thing you can do is get behind all the ones you are considering, then you will really know what works for you.