At this point in time, investment in 4k is not recommended. Every 4k screen on the market will see it's value drop in the toilet once the new AU Optronics Display Port 1.4 capable screens come out (4k, IPS, 144 Hz) this April / May with ULMB and "G-Sync HDR technology".
The new monitors have full HDR10 support, increased brightness, superior contrast and the Quantum Dot color filter technology will provide a much wider resulting in 90%+ DCI-P3 color space coverage for increased realism / color saturation.
The LED backlighting has 384 individual lighting and local dimming zones which mean darker blacks and a large increase in contrast; brightness will exceed 1000 nits which compares to < 350 for screens available today.
The Acer (Predator XB272-HDR) and Asus (ROG PG27UQ) have models coming out shortly. If ya don't wanna wait, I'd prefer 1440p Acer XB271HU or Asus PG279Q over any 4k 60 hz screen
As to the build .....
CPU - 7600k if just gaming, $7700k if you will be using any workstation apps or just have the extra cash to spare
CPU Cooler - Noctua NH-D15 ... or. if you want water. or just can't stand the fugly Noc fans, Swiftech H240 X2
MoBo - Gigabyte Z270 Gaming K7 / MSI Xpower if money's there
Memory - 2 x 8 GB of 3200 CAS 15 ... no sense going lower as price difference negligible
SSD - 250 GB Samsung Evo
HD - None
SSHD - 2 TB Seagate ... 50% faster than any HD in gaming
Case - Enthoo Evolv Tempered Glass..... combines superior features and performance with unequaled aesthetics .. Enthoo Luxe tempered Glass if ya want an optical drive
PSU - If money is there Seasonic Prime Series ... liklely an 850 watter for the Ti as if ya want 60 fps at 144 Hz, you will at some point want two cards . EVGA G2 / G3 / P2 if need to cut budget
GFX - resist the urge to rush out an buy a FE / reference card.... wait for MSI / Gigabyte or other models from AIB models. EVGAs new iCX cooler may eliminate many of the VRM and other cooling issues problems we've seen on the SC series over the last 6 years or so.