P
I also have an ATV3 which I rarely use anymore, it's now not much more than a hockey puck.
Its not hard to achieve all the things you ask for, the problem is Apple, they want ALL your money not just dribs and drabs. I have a Samsung Blu Ray player with WiFi and USB port, it does all the things you say and more for $160.What I don't really understand is why we can't have an ATV to which external hard drives can be attached and that is compatible with all the main music and video formats (especially with mkv)? Surely this is not something difficult to achieve?
I have the WDTV which is compatible however is so damn slow and freezes so often that it gets annoying.
I also have an ATV3 which I rarely use anymore, it's now not much more than a hockey puck.