This should probable be in the Hardware forum: Hardware Forum
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Just a thought: you may want to at least have your C: drive on an SSD, preferably Samsung 850 pro 512 GB. Just a thought.
here is a recent thread, you might find similar to your situation. New 4K Video Editing System Selected Parts Review
you are right about the machine you listed, its for gaming.
the main thing about cpu's today is that intel has just about hit a brick wall with speeds and has been turning to core counts to make up for speed improvements. therefore you need to consider a cpu with more core's for good performance, such as 6 core, 8 core, or more. the i7-5820k or 5930k 6 core will be good for some 4k work, but the 8 core i7-5960x will work better for difficult 4k media/projects. those i7's are on the "extreme" platform, using the x99 motherboards. these have somewhat lower default clock speeds, like 3.5ghz etc, but overclocking will get the most out of them.
several folks here still use win7 with good results.
unless there is a special need for the 12gb titan x, most people do fine with the gtx 980 ti 6gb. it performs somewhat close to the titan x, but is alot cheaper. if the project/timeline is mostly HD, a gtx 970 should be powerful enough.
for the power supply, 850w gold is good, but gold or better 1k watt is better for overclocking. evga gs, g2, ps, p2, and t2, seasonic x and platinum series, or any gold rated XFX brand are good options. the corsair RMi or RMx are ok, but the RM series without the i or x are not good models. corsair AX series is also good.
all-in-one liquid cooling is better for max overclocking, but if doing light to medium overclocking an air cooler is better. something like the noctua d15 will be quieter (no pump noise), no risk of leaking fluids, and if it breaks just needs a new fan vs whole new cooling system.
for memory, ddr4 2400mhz or higher in a set of 4 sticks.
for storage, there gets to be many options.
if they will be using after effects and disk cache or premiere preview renders, it will be best to have a dedicated ssd for that.
were you planning on building a raid with the hdd's or just running separate? for different uses or all for media?
also, "enterprise" hdd's are a bit more expensive but also more reliable and better for raid.
if they know roughly how much space they will need for project files, a large ssd or two will perform much better for the media drive(s) than hdd's.
Thanks for that. Good reply thanks again