John,
The Leupold Vari-X III, 1.5x-5x, 20mm objective lens, is a fine scope on a double and there are scads of used ones for sale. I have 5 of them, that's how much I like them. However, on my last two doubles I have gone to the Leupold Vari-X III, 1.75x-6x, 36mm objective lens. It is so little larger or heavier, as to be negligable, yet that larger objective lens gathers more light and seems to give me a few minutes of extra shooting light at each end of the day. Again, I see quite a few of them for sale on e-bay.

Best,
Ron Vella.