As for the hardware, I just ordered parts very similar to this. I haven't built it yet, though. I would also consider a mb that had the new m.2 gen3x4 slot, and get the Samsung SSD Pro instead of what is listed here. I believe the MB listed here supports it. The price is about 20 bucks cheaper and it is the latest and greatest. http://www.newegg.com/Product/Product.aspx?Item=9SIA4P03H20193&cm_re=ssd_m.2_samsung-_-20-147-467-_-Product. the speed is 4-5x normal SSDs over SATA3.
As far as I am aware, there are no 4k monitors that deliver over 60 hz. From what I gather, the Display Port cannot handle that much data. So in order for that to happen, there has to be some new technology to hit the market and be implemented in the monitors. I have not read about a 4k IPS 144hz with low gtg, with g-sync or free sync in any size monitor for any brand. So, you will need to decide whether you want 4k or 144 frame rate.
I ended up buying the Acer XB270HU bprz (http://www.newegg.com/Product/Product.aspx?Item=9SIA2F834N4239&cm_re=acer_monitor-_-24-009-742-_-Product) over the new ASUS ROG PG279Q due to availability and the numerous bad reviews on newegg. From what I have read, ACER has an update to this monitor out there, but it isn't available on Newegg yet. I saw it for around 1100, which is beyond my budget anyway.
Decide on the graphics cards at the same time as the monitor (get AMD and free sync or nvidia and g-sync). Just don't mix and match this. The free sync version of the monitor is about $100 - 200 cheaper and g-sync. Thus, going free sync means you could spend $200 more on the graphics cards.