Best streaming AND local playing box

Right now I have a Boxee Box which is great for playing local files from a NAS (Synology DS111) with a very nice UI but the streaming options are not great, and development has stopped on the Box.

I was considering the Roku 3 for its streaming options (Amazon Prime/Instant is a big plus), but after some research it seems that local playback is not well supported, and Plex needs a server and not clear if you need to connect the NAS to a PC or not for transcoding, etc. I want a simple setup, where I can leave the NAS connected to the router and have a box play files from it.

Is there a good box out there, that offers a simple user experience like Boxee or Roku, without the hassle of intermediary devices? One that offers a great local playback experience and all the major streaming services (HBOgo, Amazon, YouTube, Hulu, Netflix, etc.)? A babysitter/parents approved experience a big plus...

I'm not going to cut the cord yet on cable (yet...), but want this to supplement it.

Would GoogleTV do what I'm asking? I know they have really stalled, but maybe the rumored new device would do all this?