For starters, consider stepping down the Leupold ladder to a VX-2---the light transmission should be almost identical between the VX3 and the VX2, but if you can get the VX3 at VX2 prices, go for it!

You can go to the scope rack at a store like Academy, look through each one, and see if you notice any difference. If you do this, compare it to the Vortex Viper in 4x12x40 or 6.5x20.50 (VX-3 equivalent), Vortex Diamondback (maybe between VX-2 and VX-1 equivalent) and the Nikon Monarch 3 (VX-3 equivalent) and Nikon Prostaff 5 (VX-2 equivalent).