.22 rimfire? You speak of 400 yards; are you going to buy a centerfire rifle? Typically, a .22 rimfire is zeroed at 50 yards, and shooting at 400 yards is an exercise in futility.
Zeroed at 200 yards, a .220 Swift will have a drop of around 15" at 400; a .30-'06, 22". Any scope of whatever power won't help much unless you know the range reasonably closely.
One test for the scope you now have would be to shoot one shot at 25 or 50 yards while set at 9x; then fire one shot at 3x. If the hits are within 1/2" or so, be happy. If they're three inches or more apart, your scope ain't very good.
For coyotes and deer, which are mostly shot well under 300 yards, the advantage of anything over 4x is largely psychological. For prairie dogs or ground squirrels, more magnification is quite helpful. In general, for hunting, the field of view is more important than magnification.
Simmons and Burris are apparently of reasonable quality for the price, generally. People who use the higher grades of Tasco are commenting favorably.
For four years I've had good service from a Simmons 44 Mag; $100. I bought a rifle which had a Tasco High Country 6x24; it shoots to the same point of aim at 6x as at 24x. Other than those, however, I have Leupolds...
Hope all this nattering is somewhat helpful...
Art