You need to realize that NV isn’t just a device you buy and play with and your done but it’s just one part of a system.
-NV (single or duals)
-How will you use them? Helmet to most common but not the only way.
-Need a mount to attach to helmet.
-Need an adapter to go from the mount to the NV device.
-What will they be used for? Are you walking around stargazing or shooting?
If shooting now it brings in optics and IR lasers and IR lights.
-If shooting, what distances are we talking? Anything 75+ yards is going to make most civilian IR illuminators suck with a few exceptions like the D2 and MAWL.
-Lasers and lights now bring in mounting options and switches.
Your budget and needs will dictate what kind of gear you should buy. Even with lower quality/budget gear it’s difficult to get into for under 3-4k for a PVS-14 and related kit.