If you're not much of a reader you can watch the video of the build here: http://youtu.be/TXiE9mwUt50
This is my HTPC build. Let me start by saying I got lucky. A good chunk of the PC parts I got for free and all of the audio parts were birthday or christmas gifts from over the years. The parts I actually purchased have the price at the time I purchased them. No, I didn't buy a 6870 for $150 yesterday; that was almost two years ago.
I didn't really set out to build a HTPC, but the parts just kind of fell into my hands. Also, even though no one will ever see the inside, poor cable management is quite a pet peeve of mine (and probably most people on this site), so I like to take a few extra minutes to tidy things up.
CPU: A friend of mine bought a pre-built from IBUYPOWER and wanted to upgrade to an i7. He was in school for video production and needed the extra power for rendering. I bought his old chip for a steal. (I know, I know. Friends don't let friends buy pre-builts.)
Motherboard: Simple and reliable. Doesn't have all the bells and whistles, nor do I need them. I could have gone back to h61 or z68 but the price difference wasn't worth it. Board works for what I need.
Memory: My dad is an IT/Sys Admin for an electric company. They have a sea of old parts (most of them useless to any computer from this decade) but for a stick of ram, it's the right place to look. Note: I'm not sure of the exact model, I just know it's Kingston and I got it to run @ 1333 MHz.
Storage: Again, found this in the computer graveyard at my dad's office. I'll be looking to upgrade in the future, but most of the shows I watch are online anyway.
Video Card: The card from my last build. It has been sitting in the closet for a year or two and was perfect for the rig. This GPU is also what makes this HTPC a Steambox. It can run most games at 1080p @ ~60fps - perfect for some couch gaming.
Case: I would have gone with a HTPC specific case, but I don't really have an entertainment center to stick it in. This case was cheap and sleek, so it works as intended.
Power Supply: This is were I may catch some flak. It was cheap at Micro Center. That's about the only argument I have. If I really tried I could have probably found a better option. Nonetheless, no problems so far.
Optical Drive: My last roommate had a PS3 and we never once watched a Blue Ray. Like I said, most of the movies and shows I watch are online anyway, so no need to spend the extra cash on a BR player that won't get used. Once again, I pulled this from an old graveyard computer.
Wireless Adapter: Another dad special. Works okay for movie streaming, but that's about it. This will probably be upgraded in the future. Any recommendations for a PCI 1x card are welcome.
Here is were the build gets a little odd.
Expansion Cards: Luckily Firewire 400 cards haven't been completely swept off the planet. I know Firewire is still used in some audio & video production, but I didn't have much confidence in compatibility when I bought the thing. The card fired right up and works like a charm.
Audio Interface: The Firebox I've had since highschool. It has survived many years and was a much better option than buying a soundcard.
Speakers: I've had these monitors for a while now, but I haven't had much real estate on my desk for them. They sound pretty good and are great for movies and music. It's nice having a way to interface them in the living room and to finally get rid of my old crap-tastic all-in-one home theater unit.
I feel like I made out like a bandit on this build and it works perfect for what I need. I'm always curious to hear suggestions, so let me know what you would have done!