micro ATX $752x2gb DDR3
$25Media Center Remote
$25Quiet SeaSonic PSU
Hard drive... Not sure if he is going to store media on this or on another system...$100
Case, I would suggest just looking at Newegg or similar at HTPC cases. I would choose either Silverstone or nMedia $80Rii mini keyboard with trackball
Now if you want to go linux with like XBMC or something I would switch to the Intel g620 (unless you need 3D). Which could drop the system about $20-30
This computer will play any movie you throw at it.
What is his speaker/stereo setup? Does he have a receiver with HDMI (if so no sound card is needed)? Does he just use his TV, Logitech, or sub $500 speaker setup (if so no sound card is needed)?
The way I set up a HTPC for myself or friends is..
What are you going to be doing? Movies, 3D, music, netflix, hulu, gaming
Then I choose my case that I want to try, looks good or mod? I say mod b/c I just made a ITX htpc out of an old Xbox1
What kind of stereo set up? Nobody I know will have a 4k+ stereo to ever consider a sound card and every new system you build can support the new audio formats.
What OS are you going to be using? Windows 7 or some flavor of linux
Then I choose my parts. Lately either Llano or g620 (i3 is way overpriced for htpc but g620 can't do 3D). I will then know if I need to go ITX or mATX since I choose my case.