See the Assassins Guide (a blog referenced on this forum). It has the details you need for this project.
Here are some items to think about as part of your planning:
How many drives are you going to need?
* Bluray movies are around 20-30GB+ uncompressed. With Handbrake some compress to around 5GB. I like lossless video and music so I don't compress. So around 33 BD's per TB or roughly 100/3TB drive. If you have 500 BD movies then you will need 5x3TB drives.
* DVD's are smaller 4-8GB so ~166/TB so 1,100 DVDs would fit within ~6.6TB (or 2 drives if you use a 4TB
What case is needed to house your drives + growth?
How many SATA connectors and power connections and power is needed to support the drive count?
See the FLEXRaid thread on this forum for a 10+ drive solution
Don't forget about DATA PROTECTION. If like me you have hours of time invested in audio library w/tags then you dont' want to rebuild so backup the music. You may be willing to risk losing a drive of video so mitigate the risk with something like a snapshot RAID (i.e. FlexRaid). Assume the drives will eventually fail....it's just a matter of time and hopefully you catch them so they fail only one at a time.
2. LOCATION & NOISE
* Will the computer be in the listening/viewing room or a closet where you won't hear the fan/disc noise?
* If you need a HTPC in the HT then you probably will want to build a quiet client connected to a server located where you can't hear the fans/drives.
* I have a server in a closet with HDMI through the wall to pre/pro so noise isn't an issue
3. Client + Server or combo
* The above two items will support a decision of either having one giant box or two boxes (AV-component like box in room, with server in IT closet)
4. You can then pick the Motherboard/RAM/PS/Video parts
5. OS decision (win7 or latest win8.1)
* if you want Remote Desktop then you need Pro version
6. Front end SW for media mgmt and playback
* See this forum for a SHOOTOUT thread with pics of all the major options
* Note Windows Media Center is no longer free with Win8.1
7. Ripper for movies (i.e. MakeMKV free or AnyDVD HD for a fee) + ripper for music (i.e. JRiver, dbPowerAmp, EAC) + ripper for DVD-A & BluRay Audio if you want (DVD Audio Extractor) + SACD (advanced - PS3 hack)
8. remote control (lot's of options--especially if you have these devices for other reasons)
* Handheld remote (I use an old HP Media Center remote with USB wireless eye)
* I also have a Microsoft wireless keyboard (and a blue tooth KB I actually use with my office PC)
* I also use a laptop w/Remote Desktop for audio control
* Androi and iPad tablets are useful as well
Another option is SERVER + WORKSTATION/CONTROLLER + RENDERER (uPnP / DLNA)
* Build a Media Sever and stick it in a closet on the LAN
* Use a laptop or tablet or office PC as Workstation for control
* Use an Oppo 103 as renderer connected to TV (I think Video game consoles like XBoxOne do this, too) - you can pull content from the renderer or push from server using a workstation such as office PC or tablet/laptop
* You need to think about the media mgmt ease of use implications of this. I have used with good results JRIVER but I'm not familiar with the other options in this setup.
Another option is the glitzy COLLECTORZ Movie Data base. You can browse that like an HTPC but once you are ready to HIT PLAY you simply go to the shelf the dbase points you to, grab the disc, put into player and hit play....from there the experience is the same or better than HTPC
PLUS you don't have to manage a multi-drive IT system filled with movies that get watched once per decade
DVR & Streaming Services are topics others can discuss. I use my FIOS Set top box for DVR. I use my TV or Oppo w/Roku or game console for streaming (Netflix & Amazon Prime). I also have music services on my PCs (I subscribe to Zune/Xbox Music but have considered flipping to MOG or Spotify).
Transcoding for tablet/phone/etc playback is another topic.