1. mede8er players are the current best value for money (at least in Europe, it seems that in the US their pricing is the same as the A400...). Med are also the most stable of the 3.
2. plex is not a media streamer, it's just a DLNA media server that needs a player at the other end (but this can can be many things from any media player to a smart TV)
3. yes, except form factor the x3D range shares the same specs and same firmware across all models.
4. same as gusgus :...