looking for a new scope for my varmint ar and have pretty much narrowed it down to these three.vortex viper 6.5x20x44 millett lrs-1 6.5x25x56 leupold mark ar 6x18x40 i know there are much better scopes but these are in my price range and have the features i like (except the 1" tube on the leupold)i really need to keep this under 500.00 buck so opinions?...