About the best advice I can offer is, buy a fixed power scope. I know variable power sounds neat, however vpower scopes aren't as clear when looking thru.
I have a Bausch & L, discoverer. At 500 yards you really can't judge a deers antlers well at all. If it were me I would spend way more money, try to find a Kowa fixed power used, run you about 600 or so. You might want to check out some bird watching forums, or long range rifle forums.