Re: Nikon Monarch X vs. Sightron SIII
rcr, I have all of the scopes you mention above. Optically, i.e. quality of image, I would not put the Sightron SII, which I think has been replaced -- model-name-wise -- by the 'Big Sky', in the same category as the others listed.
However, in other, perhaps more important, categories, like repeatability, tracking, dependability, and durability, the SII does not take a back seat to any listed.
In my opinion, quality of image is not as important as the other factors, presuming the optics are "good enough". And the SII optics are certainly adequate. The SIII (S3) optics are better than any of those listed, at least in my opinion. On a par with Nightforce NXS.
If you want a recommendation for top value in a modestly priced scope, you should take a real hard look at the Sightron SII4-16x42MD. That was, and is, a really good scope. I've used one for ten years, and I wouldn't sell it for double what it cost me. Because I *know* it performs.