In that range, you'll have lots of quality glass to choose from. Nightforce or a Schmidt & Bender would be my first choice. Magnification is a bit trickier. Depending how long you mean by long range target shooting, you may be better off getting 2 quality scopes with QD rings to change off between hunting and target shooting. Most common variables in hunting rigs are generally, 2.5-8, 3-9, 2-10. My variable hunting scopes max out at 12x or 14x, with some less. If you're shooting long range, guys commonly end up with a 20x or 24x top end, some less and some more.
A 4.5-14 would be middle ground I would think if you were set on only one scope. Don't know if that gives you the top end for your long range work - again it depends on what ranges and what type of shooting you're planning. You can get a couple of Zeiss Conquests or Leupold VX-III's in two different mags for a couple of thousand bucks and both are very good quality scopes.