Amazon's Fire devices are cheap and work very well, and if you have an Echo, those can now work together too (so I hear, I don't have either myself).

I set up a Fire Stick for my Mom, and my only complaint is that (IMO) the UI is a mess in the same way the Amazon Video app is a mess on other platforms, but I suppose once you get used to it, it's fine.

Google's Chromecast Video pucks are also cheap and very good, but they don't support Amazon Video - that's a show-stopper for many folks (including me).

Same for Apple TV - no Amazon, but it's apparently coming via a software upgrade later this year. Apple TV is ridiculously overpriced though - I can't figure out why anyone would buy it, given the myriad of cheaper and more capable offerings from just about every other player in the game.

Netflix is available on all of those devices.

I use a Nvidia Shield these days, and am really liking it - it's the first Google/Android streamer that natively supports Amazon Video without any weird nerd hacks, so that's a win.

I don't use things like Plex or Kodi, but Shield apparently offers excellent support for those sort of media home-server dealios, if that's your thing. Shield has a ton of gaming options, if you like that.

Shield is also not among the cheaper offerings, but I think it at least offers a lot for the price.

Happy hunting!

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Do not taunt Happy Fun Ball

Nvidia Shield plus Kodi. Even with out Kodi you can just about get every streaming service there is with it. Now all they need to do is add a blu ray player and would be set!