I used a Weaver Grand Slam Tactical 3-10x (a $300 scope with tactical/target turrets and a mil-dot reticle) for my first three years. It obviously doesn't compare to higher end glass, and would only allow me to spin up to about 750 yards on a flat base, but it worked well for me at the 100-650 yard distances I was accustomed to shooting during that time period. So, if you already have the scope you mentioned, and are somehow budget-limited out of another scope, I'd suggest you go out and give it a try to see what happens. However, if I'm not mistaken I believe the scope you have uses conventional hunting-style turrets, rather than a graduated tactical/target style turret that you can adjust for ranges beyond your zeroed distance. As such, it may prove to be very difficult for you to use that scope in the field for shooting at a variety of distances when elevation adjustments are required (in other words, when shooting at distances beyond your maximum point blank range).
As far as employing the "calibrated drop" style reticle you described, I've rarely found that scopes with hash marks for various distances actually correspond to the bullet drop you get in the real world. Think about it: for that "600 yard" mark on the reticle to match the drop of your fired bullet you'd need a bullet, velocity, and conditions that were virtually identical to whatever the scope manufacturer chose to test when designing that reticle. Because of that, those hash marks usually only give you a ball-park figure in the real world, rather than an aiming point that would be as precise as dialing a certain amount of elevation to compensate for the drop of YOUR bullet, from YOUR gun, in the conditions where YOU are shooting. That's not even to mention the effect that wind would have on your bullet, and the need to compensate for it at distance. I was shooting this afternoon under windy conditions that necessitated about 24 inches worth of wind correction at 550 yards (we weren't measuring via the inch system, but that's a number that most people can more easily visualize)... now imagine the trouble you would have guesstimating hold at that distance when you really wanted to get your shot on target.
Still, there's no harm in playing with it if you already own it! As for the magnification, I've made hits beyond 800 yards with 10x magnification, and I've shot at 6 and 8 inch plates at 600 yards with 3x magnification... some people have shot far beyond those distances with magnification less than 10x; and some folks have done very well at that task.