Sorry for taking a bit to get back to you, have been busy today. In any case here's a proposed build for you:
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i7-5820K 3.3GHz 6-Core Processor ($351.98 @ Newegg)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($24.89 @ OutletPC)
Motherboard: ASRock X99 Extreme4 ATX LGA2011-3 Motherboard ($174.98 @ Newegg)
Memory: G.Skill Ripjaws V Series 32GB (2 x 16GB) DDR4-2400 Memory ($139.99 @ Newegg)
Storage: Samsung 850 Pro Series 512GB 2.5" Solid State Drive ($217.97 @ Amazon)
Storage: Western Digital Red 4TB 3.5" 5900RPM Internal Hard Drive ($149.00 @ B&H)
Video Card: Gigabyte GeForce GTX 970 4GB WINDFORCE Video Card ($317.99 @ Newegg)
Case: Fractal Design Define R5 w/Window (Titanium) ATX Mid Tower Case ($109.99 @ Newegg)
Power Supply: EVGA SuperNOVA NEX 650W 80+ Gold Certified Fully-Modular ATX Power Supply ($69.99 @ NCIX US)
Operating System: Microsoft Windows 10 Home OEM (64-bit) ($87.95 @ OutletPC)
Monitor: Dell U3415W 60Hz 34.0" Monitor ($779.85 @ Amazon)
Total: $2424.58
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-03-21 00:31 EDT-0400
To briefly summarize why I chose what parts I did:
CPU - Premier will use all of the cores that it can take so having a 6 core system makes sense. This will help keep your render times within reason.
Motherboard - Solid choice with a good feature set
Cooler - Just need one since the 5820K does not come with one, this one shall suffice just fine.
RAM- Premier also loves having RAM and 32 GB isn't terribly expensive
SSD - This helps improve overall performance and helps the system feel more responsive
HDD - 4K video files are obviously going to take up a fair enough space so you'll need someplace to store the finished product once you've done the work needed on the SSD
GPU - While not top of the line (with the budget you have in mind) it should suffice just fine unless you decide to play games in 4K, then we'd have an issue
Case - Really a personal choice but I really like how clean the S5 is especially if you exercise good cable management which really isn't hard with this case
PSU - Solid gold rated PSU that should handle all of the components without an issue
OS - No reason not to go with Windows 10 at this point in time
Monitor - I'm presuming that you don't already have a monitor which is why I included one in this build. It sounds almost like you intend to do this professionally and Dell is close to the gold standard when it comes to monitors being used professionally in video editing. There are some better ones out there but they're way outside of your budget. This monitor, once calibrated, should suit your needs just fine