Is a Blu-ray player entirely out of the question?
I ask this because I use a Samsung Blu-ray player through the network. The only requirement is that the computer run a DLNA media server.
Plex works well for AVI files, though I've had issues with MP4 files.
Nothing appears to be a perfect solution, amongst dedicated media players.
The only "perfect" solution is to directly connect a computer to the TV. For example, a Mac Mini for about $600
I've done that too, and liked it quite a bit.