There are also some good thoughts on X-Plane performance on their developer
blog, I read up on this stuff pretty extensively as I was planning my build and while a lot of it is from a few years ago but is still good insight in to how the rendering engine works and how settings and different hardware affect performance. You've got to read between the lines a bit but it's in plain enough language that you don't have to be an engineer to make sense of it.
This
article is really useful for understanding how X-Plane uses your hardware.
What I personally took away from all my research though is that it's still possible to set X-Plane up in such a way that it can bring current top of the line hardware to its knees through combinations of settings, scenery, aircraft models, etc.
The specs on that system (aside from that PSU, seriously) are more than sufficient to have a beautiful X-plane experience and if I remember tonight I'll try and get a screen of my actual rendering settings and maybe a few screens for reference.