For anyone looking at running retro roms, Lakka seems to be a fairly good contender. It runs on a variety of platforms including the android tv devices.
The interface looks and feels much like the PS3 and has several emulators to run anything from master system to snes and playstation one.
The intel nuc appears to be the device of choice for these things and i will be setting one up soon. They are on ebay from about £90 but they are a good all round machine. For cheaper devices, look at the raspberry pi, there is a build for it, and you can get a case looking like a nes or megadrive.
I would go so far as to say that all the retro machines coming out of sega and nintendo recently are built in the same way.