This is a build that I made for a friend of mine that does Twitch streaming. It was made with the intent of replacing her aging Laptop (which she currently streams on), it had to be small form factor AND it had to be under $500. I got pretty close to meeting the $500 goal but in the end it was worth going a bit over budget.
CPU- Originally I had my eyes on the Pentium G3258 because of it's awesome overclocking capabilities for gaming (for a cheap CPU) BUT I had to remind myself that this isn't a GAMING rig... I went with the 4130 because it's still a cheap CPU but it has hyperthreading capabilities which will be important for streaming/multitasking.
Motherboard - Went with the ASRock H97M because it was the cheapest, most reputable brand I could find that had wifi built in.
RAM - I've used the Kingston Fury sticks in another one of my builds and love the amount of performance you get for such a low price. Plus, they're clean looking!
Storage - The WD Green works out because it doesn't need to be a "fast" "gaming" drive, just something cheap and reliable that can hold a decent amount of data.
Case - This was probably where I spent the most time researching, I needed a small form factor case that had a built in PSU, the ability to mount a slim DVD/CD drive AND not break the bank. Went with the silverstone SG05BB-450 because it had the best reviews and fit the bill in all of the above areas.
Optical Drive - Just a slim Samsung DVD/CD drive, cheap but necessary.
Capture Card - We decided on the Avermedia Live Gamer HD because it was cheaper than the BlackMagic Intensity Pro that we currently use in my wife's streaming PC and had similar capabilities. It's also very user friendly and widely compatible with different streaming software, in contrast to the BlackMagic which tends to be very finicky with lots of hardware and software incompatibilities.
And that's it! Feel free to ask questions and post comments below!
P.S. Here's the link to her Twitch Channel http://www.twitch.tv/shiva_goddess