Just because it is by a certain brand doesn't automatically mean it is a good product, for all you know they could be using some crappy manufacturer. Toms hardware does a decent table showing who uses want:
http://www.tomshardware.co.uk/power-supply-psu-brands,review-33002.html
But yes, generally EVGA are good regardless.
The xbox one x CPU is far more future proof, may not be super powerful IPC/clock speed wise but 8 cores is the way gaming is heading and as mentioned above with dx 12 baked in, games will get more out of that cpu than a dual core especially when developers will only have the one platform to optimise for.
As for how much better optimization will be down the line, I be willing to say quite a bit better as games still look very good on the normal ps 4 now especially the exclusives such as HZD, LOU.
If you where to take a PC that matched a PS 4 back in 2013, which would probably consist of what.... a 7850, Athlon X4 760K (probably more powerful than the PS 4)? And then look at how it performs in games nowadays @ 1080P, it would not be doing very well at all. I came from a 7850 to a 290 due to having to reduce a ton of settings just to be able to get near 60 fps and that was 3/4 years ago so imagine what it must be like for all the titles from the last year or 2....
No doubt if you want a PC for gaming for whatever reason like badly wanting free/g sync, high refresh rate, 21.9 or something else that PC offers over consoles then what you specced is a great gaming machine for 1080P but to me..... if you want to do PC gaming then you do it properly to get the main advantages of better graphics and/or better performance and in order to do that, you need to be spending a min of £800 imo.