500 yard shot with a 30-06 is a stretch, depending on bullet weight. But not a round known for distance and accuracy.
I have had a 30-06 since I was 14 years of age and am now knocking on the back door of 40, so I do know about the round and it's capabilities. But while it can shoot at 500 yards it may not be the most accurate among other choices out there for the distance stated. I have killed many of deer with it and some at some good distances, but I am more familiar with it as a hunting rifle using heavy bullets (150 and 185gr). In which the drop on those 2 are substantial at longer distances. So my info is more along those lines of a hunting round.
A good rule of thumb for getting a "good scope for my XXXX rifle"
Competitive shooters will tell you that you should be prepared to spend as much on glass as you do on your rifle.
The difference between a Leupold and an NcStar will be like night and day.
Don't skimp on the glass!
-J-