I don't know if you've heard recently but the AMD 390x is suppose to destroy any Nvidia card. I have a GTX 970 at the moment and I am not impressed. I'm waiting for the AMD card to come out in possibly June so I can run 4k at ultra settings.
What I recommend:
For high performance at a better price go for an AMD card.
As for Nvidia they're meh and really expensive. I does really count down to what you're going to be doing.
.. GTX 970s really do suck... Just no.
I also have a AMD 8350 as a CPU. Not only does it have very good price to performance, it gives me no issues, I've also never used more than around 48% of my CPU running at 4K so far. Intel, well.. I'm speaking a little bias but people fan-boy over Intel way too much. It's overpriced and it's not necessary for 'gamers' to have a $1000+ CPU.
People are too focused on having a Intel CPU because they think it's 'cool' and that their systems will be better because of it when in reality it won't do jack poop for gaming. Maybe if you're an architect rendering models maybe so?
Back to the matter, look up AMD API (Mantle). Having a AMD CPU and a AMD card, that can really optimize your system.
Some advise: Do your research!!!! Watch reviews, get some benchmarks, compare specs, and see for your self what you really need. Having DDR4 RAM with Intel's I7 may be a big improvement on RAM but really.. You seriously DO NOT need that. Unless you're a speed hog that wants a 0.0001 response time on your system you might as well just burn money xD
I wish you luck on your system! And a $90 PC running 1080p Ultra is a lie... Even the graphics card it's self would have to cost more than that