The fastest low-cost networking board right now (that I can find) is the espressobin, built around the Marvell Armada chipset. It's got three full-duplex GigE ports that can actually run as such as well as pci-E and SATA. Unfortunately it's oriented toward routers and stuff so it lacks HDMI, so no good for home entertainment.
Problem with these: I can never be sure what level of acceleration for video playback is supported - and in what quality. The Pi is pretty rock solid in that department. Also, the Pi has by far the biggest community and extensive documentation, and I can rely on there still being Pis available in years, compared to the Chinese outfits where no one knows how long they'll stay in market.
Also Pine64[2] is supposed to be suitable for HTPC (Kodi) usage but I haven’t tried it and YMMV.
I <3 RouterBoards + MikroTik.