How's a $300 full-HD media-playing PC sound to you? The big plus of this minuscule Habey BIS-6620 ultra-compact PC is its total silence, playing back 1080p video with no fans. For that price, though, you don't get a hard drive, but there's a place to plug CompactFlash and SD cards in the front, and there's a 1.8-inch internal hard drive bay inside. You can load up any flavor of Windows or Linux, too.
It's not perfect. You'll need the 6620-II for a DVI output, because the base model has only VGA. And you might need to use one of its USB ports for outboard surround sound. If you can overcome those hurdles, though, it might be a kick attaching this to the back of your HDTV and using a real PC in your home theater instead of some crippled and restricted box.
Here's a video, giving you proof of its smooth, hardware-accelerated 1080p playback: