Do you wear glasses? *Any* sort of glasses!
If so then you had better make certain to check out the `eye relief' of any spotting scope you have any interest in. *Especially* at the higher powers! From *my* own experience the majority of the spotting scopes in the lines / brands you've listed just *didn't* have enough `eye relief' to be useable with glasses, of *any* sort, and there were models where even at the lowest power the lenses of my glasses were banging into the eyepiece.
If you are lucky enough to find a dealer carrying the Swift line of spotting scopes you'll find that they have two models that can use zoom eyepeices that have `extended' eye relief and one of them comes close, it only exceeds your approximately $100 `limit' by about $200 {WAN GRIN!}, to the unrealisticly low limit you've set. (As with all optics you *do* get what you pay for! And a spotting scope that is selling for around $100, no matter how `glowing' a recommendation one may hear for it, is just that a $100 spotting scope. You may or may not be able to discern a .22 calibre hole in a piece of paper at even 50yds let alone 100 yds and a .308 calibre hole at 100yds may be as bad as the .22 calibre hole at 50yds. [Been there, done that, and learned my `lesson'. {FROWN]]) The Swift is going to be the `cheapest' `quality' spotting scope you are going to find.
The `top of the line' Swift *and* the Leupold varible spotting scopes are the `next step up, and *that* step is up to around $700! (But then, like I said before, you get what you pay for.) With those two you get detail `resolution' that will enable you to see a .17 calibre hole in paper at 100yds almost like looking at a .45 calibre hole at 25yds! You *won't* be banging the lense(s) of you glasses, or sunglasses, into the eyepiece and your eyes won't end up being tired after even looking through it almost all day! (With the *cheap*, IE: "Around $100 or so scopes" your eyes will be screaming for mercy after maybe a half hour or so.)
Now... You *could* get rediculous and pay even more than around $700 or so for a spotting scope but, for the most part, after that level you are only paying for a glorified `name' and not much more. (After just so far there is much more they can do to `improve?' the optics beyond writing fancier descriptions in their ads. {WICKED GRIN!})
But! But! You splutter and choke! I *don't* know *if* I am going to use this all that often! Hee! Hee! Hee! Actually you'll, *if* you get a *quality* spotting scope, be finding *all sorts* of uses for it. I've used *mine* for observing total and partial eclipses of the moon, watching and identifing assorted birds, (With and adapter and it was actually very inexpensive.) used mine for a long telephoto lense, followed `slurry bombers' dropping chemicals on a `wild fire', watched them clean up an accident scene about a 1/4 mile away from my house (The accident, btw, took out a power pole that supplied power to all the houses here on our farm along with quite a few other people in the area!), along with helping me `spot' shots when sighting in and when shooting `pasture poodles' that were destroying my hay fields and pastures. I've also taken mine with me whenever we go out in the fall to `go look at the fall colours' up in the mountains. And actually found it to be a nice `adjunct' to a good pair of 7X50 binoculars. (Locate something with the binocs and then get a good close look with the scope.) A good short and a good long tripod is a very handy combination for *both* the spotting scope *and* the binocs. Even my 4yr old son can look through either one without any problems *and* you don't have to worry about them being dropped or knocked off whatever it is that you are trying to show. (E-mail me and I can give you *a lot* more reasons for owning a *good* *quality* spotting scope. [And binocs.])