Alan,
I think you will find the D-740 to be a very capable NV riflescope regardless of what Gen 3 tube is inside of it. The MX10160 tube is simply a tube that does not have the capability of manually adjusting the gain. For hunting purposes (unless you hunt in street lighted areas) you will never need to adjust the gain anyway. Unless you already have one, you might want to pick up a good IR device to maximize performance in poor ambient light conditions (no moon, cloudy nights). Kevin