I'll freely admit I've never looked through one, but for the price the Nikon X1000 scopes don't seems all that appealing to me. I think they are jumping on the tactical scope hype train in an effort to sell for more $$$. And it's not just a FFP vs SFP debate either, because I'm not going to come on here and say that every scope needs to be FFP, period, end of story.
But, for $650 (new, no sale hunting, no used market) I'm not seeing any features that separate it from much more economical scopes, or features that make it comparable to other scopes in it's price range. It's got a 30mm tube, and has 90 moa of adjustment. 90 moa? Just looking at the $300 Vortex Diamondback Tactical 4-12x40mm (1" tube), it has 70 moa of adjustment. Then compare it to the SWFA 3-15x42mm which costs only $100 more, it has 140 moa of adjustment. The point isn't the outside diameter of the tube, it is how much internal adjustment it has.
Also, even if the glass is comparable to the current base level of Monarchs, at that price point it really isn't all the special either. Neither is illumination. I think if Nikon was bringing these scopes to market it the $300-400 price range, they would be more attractive (but still not my cup of tea).
For the budget I think we are talking about in this thread, I'd recommend staying at 10x power, or not much above. 10x goes a long way, and certainly further than the 400 yards the OP mentioned. Magnification increases the price without adding anything other than that. With SFP scopes that have reticles designed to be used at maximum magnification, 10x isn't too tight at 300 yards either, and the mirage is less distracting as well.