Also, at 300 bucks, honestly it's going to be much cheaper to set up a raspberry pi or its equivalent with some hybrid franken-software setup. Add a few batch files on watch folders for video format conversion and I think you're good to go.
http://www.logitech.com/en-us/remotes/universal-remotes/harm...
Also iirc, the Samsung Galaxy S2 tablet versions (i.e. identical to S2 but without the phone) cost around $200 bucks, and that can play any format you throw at it. Plus since it's DLNA capable you could directly stream content off your home server without breaking a sweat. The CPU/GPU are pretty capable being the Cortex A9/Mali 400 combo.
The tablet I got is a NatPC 009S. Also sold as Tabtronic and probably a bunch of other names. It's a nice little thing for it's price. As mentioned, where they've skimped the most is clearly the screen, which doesn't measure up favourably to mid/high end Android phones, and much less to the high end tablets.
Note that I've not tested 2160p output, though, as I don't have anything that can display it, and given the marketing copy on some of these sites who knows, but that's what they claim anyway.