Mule Deer has written extensively on the subject of scopes, a topic that he has researched extensively. Before you spend your money, spend a couple of hours reading what he has said about the topic.
Personally, I have had excellent experiences with Swarovski optics in low light situations (primarily hunting leopard).
You might be able to find a good, used Swaro AV or Z3 ~ $500. I would also give the Meopta line a close look (no pun intended).
