100 MOA :
Why limit yourself to just those scopes with 100 MOA or more? Did you know that a 55 gr. Sierra BlitzKing, at a modest 3000 fps, will only need 11.5 moa of turret cranking (assuming a 100 yd. zero) to be dead on? That means that any scope with 25 - 30 moa of total adjustment would suffice.
If you want to shoot at much farther distances like in the 800-900 yard range where you'll need to crank to 45 moa+/- then mount your scope with a 20 MOA base or, better yet, use Burris Signature Zee rings with the offset inserts to get your 20 MOA. I do this on all of my prairie dog rifles and I can dial in out to 900 yards (44 moa) using scopes that only have 60 moa of total elevation adjustment. I do this by dialing in 45-50 moa
down from the upper limit of my elevation turret & centering the windage turret. I then shoot 3 shots at 100 yards (using a tall piece of cardboard with a bullseye 3' above the center of the cardboard) and find out exactly where my rifle/scope combo is shooting. At that point I'll remove the scope and install the offset inserts of the proper offset (.005", .010" or .020") to bring the scope into boresighted alignment with the rifle - without touching the turrets. Once I get within 6", I'll finally use the turrets to fine tune my zero at 100 yards. At that point, I still have enough turret adj to get me to 900 yards.
"don't care where the parallax is" :
If you are going to shoot at long range distances (500 yds.), you will very definately want to have some sort of parallax adj. Unless you can keep your eyeball
exactly centered in the scope for every shot, your bullets will hit in a huge circle even while you're thinking that the scope is "dead-nuts on" at the time of ignition. To see the effect, mount your rifle in a solid vise and look thru the scope at an object 100 yards away. If you move your eye around in a small back & forth or up & down motion, you will probably not notice very much crosshair movement on the target. Now aim the scope toward a more distant object (200 - 500 yds.) and repeat the eye movements. On any non-parallax adjustable scope you'll see the crosshair move quite a bit from side-to-side or up & down.
Here lies the error by using non-adjustable scopes at over 100 yards.
6x-24x :
This is subjective - granted. I have found that my adjustable power scopes are very rarely used at the upper powers even while shooting prairie dogs at 400-1000 yards. I find that 14x-16x is an ideal compromise while being able to easily see those little grass eaters & not having heat waves (mirage) being a problem. At 18x and above the heat waves obscure the P.D.s and cause a miss. But that's my opinion and 2c worth.