something to keep in mind is that you can rarely go beyond 40x magnification during the day due to the disturbed atmosphere (ie. heat waves radiating off the ground) you're looking through. that's why most spotting scopes come with 20 - 60x zoom eyepieces. only on an exceptional or cool day will you be able to push the optics of your scope to the highest magnification.
so, that means you want to get a scope that has quality glass or lots of aperture to allow for good resolution at the lower magnifications you'll be able to use.
an excellent scope for that is the Celestron C90 Mak spotting scope. it has a larger than average 90mm lens and is what I use for the range. my friends are always fighting over who gets to use the scope when they're shooting out to 200 or 300 yards because it sees the targets so easily.
http://www.celestron.com/browse-shop/sport-optics/spotting-scopes/c90-mak-spotting-scope
a cool side feature/function is the C90 will let you look at the moon and planets, without much difficulty, which are the easiest things to see when you live in a city, because their reflections are so bright.
you have a couple of options to mount this scope as well. you can use a standard photo tripod, as on the bar (called, in telescope speak, a Vixen dovetail) on the bottom of the scope there is your standard 1/4" photo tripod screw hole, so you can secure your tripod head foot to it and snap it into place. An alternate option is to get something for tripods that uses the Vixen dovetail, like the AZ4 tripod mount from SkyWatcher. it even comes with a leg spreader that has holes to let you put your different eyepieces for various magnifications, for easy access.
http://ca.skywatcher.com/_english/02_mounts/02_detail.php?sid=50
now the scope doesn't come with a zoom eyepiece, but you can buy one for about $100 or so.
http://ca.skywatcher.com/_english/03_accessories/02_detail.php?sid=166
I know I've posted a lot of info, but I recommend this because a) I have personal experience and b) the Maksutov-Cassegrain lens system is extremely well regarded, especially in the astronomy community and is under appreciated for terrestrial viewing.