If you are going to build, this is the setup I've used several times and recommend without reservations:
- Motherboard: Gigabyte GA-Z97X-UD5H-BK
- Processor: Intel Core i7-4790K
- CPU Cooling: Corsair Hydro Series H75 Liquid CPU Cooler (you don't need liquid cooling, but it's quiet and not much more of an increase)
- Heat Sink Compound: Arctic Silver 5 HD
- RAM: 2X Crucial Ballistix Elite 16GB Kit (8GBx2) DDR3 1866 PC3-14900 (32GB total)
- Graphics: EVGA GeForce GTX 960 SuperSC ACX 2.0+ 2GB GDDR5 128bit (128-bit, 1024 Cuda cores, up to two)
- Boot/System Drive: Samsung SM951 M.2 SSD 128GB (The M.2 port in this motherboard has dual PCIe bus access for better performance)
- Scratch Drive: Samsung 850 EVO 250GB (You need a TON of scratch space for editing HD video)
- Data Drives: 2X HGST 4TB NAS HDD's NO RAID (one dedicated to video files, one for everything else, plus a pile of external eSATA or USB 3.0 HDD's)
- Power Supply: Corsair RM Series 650 Watt ATX/EPS 80PLUS Gold-Certified
- Case: Fractal Designs Define R5 or R4 case (quietest cases I've ever used)
- Card Reader: Rosewill 2-Port USB 3.0 4-Port USB 2.0 Hub eSATA Multi-In-1 Internal Card Reader with USB 3.0 Connector
- Optical Drive: LG 14X Blu-Ray Burner
- Op. System: Microsoft Windows 8.1 Pro - 64-bit - System Builder - OEM (Eligible for purchase with a new SDD, HDD or MB)
These are all components I've used several times, or updated versions of those parts, and were selected because of their durability, compatibility, performance and price. This setup also has the advantage of being able to support Mac OS/X via TonyMacX86 MultiBeast. (Most of the systems I build dual-boot Windows and OS/X.)
Yes, you might find alternatives that are faster or cheaper, but how well will the work together with other parts in a system and how do the compare in terms of reliability? I've been building these systems for over 4 years now and all are still in daily use as photo or video editing stations with only a single failure (a cheaper 350W power supply) and no compatibility problems after setup. My daughter's iMac didn't last as long as this setup without going to the Apple Store for several repairs and, ultimately, being relegated to non-critical work. Note that you can also step up to the GTX-980 or Titan if you need more cores. But one or two GTX-960's is the sweet spot for price vs performance.
Cost ~ $2,100 plus your choice of keyboard, mouse and monitors if you can't reuse what you've got. Maybe a few hundred less if you can reuse your case, optical drive and media card reader and go with 3TB HDD's instead of 4TB. Expect to pay another $500-600 if you want someone experienced to build and configure it for you.