There are tons of TV sticks and mini-pc's with Android and Linux support, but a new breed of Intel Quad-core HDMI mini-pc's have now started to appear supporting a fully-functional Microsoft Windows 8.1 OS.
GULEEK i8 comes powered with an 1.3 GHz Intel Atom Z3735F quad-core processor, 2GB DDR3 RAM, 16GB of storage, a microSD card slot, 2 full-sized USB ports, a micro USB port (for charging), a micro HDMI port, a headset jack, microphone, 802.11b/g/n WiFi, Bluetooth 4.0, 3000mAh battery (allowing usage as a portable media player without need of a power adapter), all this in a ultra-slim, light-weight and noise-free fanless design. The Intel powered quad-core CPU coupled with Microsoft Windows 8.1 OS makes this one of the best setup for a home entertainment system supporting hardware video decoding (Intel HD Graphic(Gen7)) with full codec support unlike it's Android and Linux counterparts, just plug this on any screen via HDMI and you have a fully-functional desktop computer with Windows 8.1 OS.
You can also use this as an headless system, the mini-pc comes with an Android app supporting remote login and interaction with the GULEEK i8 without requiring a keyboard and mouse.