I've built my own "HTPC" for watching Netflix, other websites, youtube, downloaded content, and some gaming. I used a Coolermaster Elite130 case as the base and then put inside what I had available at the current budget. Right now that's an undervolted i3 4130, 8GB DDR3, and a 4GB GTX 960. Not really a gaming machine in the current form but following standard component sizes allows it to be upgraded with ease later on. It's fairly small in size and can be made to run cool and quiet with the right hardware and cooling choices. There's some good ITX sized boards out there which will support higher end hardware, but you are limited to a 2 slot video card.