Hello and Seasons greetings to all!
 
I have a friend who just got a 4k TV and wants to build a high end HTPC.  This stuff he is picking out so far are top of the line processor and x99 board.  Im not really sure that is necessary or not.  He wants it to last several years.  Also how much ram and what kind of GPU would be best.  I was thinking he might need a reference design card rather than the multifan one that put hot air into the case.  And he is SET on getting this case!  He isnt really worried about price at this point either.  He will have a GPU, Sound card(ZX-R), TV card and about 4 HDD and has picked out this case  http://www.newegg.com/Product/Product.aspx?Item=N82E16811163196  .  So any help here is appreciated.  Id like to help him out but this just isnt an area i am comfortable.
 
Any help will be a great help!

HTPC as in "Home Theater PC"?
 
Then he does not need an X99 motherboard, a 4690k is fine but for future proof the 4790k is better.
 
Also since it is an HTPC, I suggest getting a maxwell GPU something like a GTX 970 or 980. If he plans to use madvr with advanced filters a single maxwell GPU even beats an SLI setup. I also heard that maxwell supports hardware acceleration for x264 hi10p and x265.
 
I suggest you read this.
http://www.anandtech.com/...force-gtx-980-review/5
 
http://community.futuremark.com/forum/showthread.php?179769-Video-rendering-finally-caught-up-with-high-end-cards-say-Hi-to-NNEDI3!
 
http://wiki.mikejung.biz/index.php?title=MadVR

I would also warn about noise. CPU, GPU, PSU and case fan noise is very noticeable when watching movies or whatever. I soundproofed my case, purchased a fanless Seasonic PSU, upgraded the case fans, and lowered my EVGA GT 430 GPU minimum fan speed with a GPU BIOS modding utility to reduce noise. I upgraded the old hard drive, which you could also hear grinding away, to a SSD. My next upgrade will be a fanless CPU and motherboard that has HDMI out.