Roku
Apple is a walled garden overpriced ecosystem. All Apple is overpriced cheap Chinese gear with a USA label. 40% Margin! Most isn't repairable easily being glue assembly to reduce the already low costs. If you don't have an iPhone there is zero value to an Apple Watch and little point to miss-named "Apple TV" (no tuners or screen, it's merely a streaming box that really needs an iPhone).
Chromecast is barely more than a wireless HDMI cable. It reports to Google and really needs a laptop or Android gadget (with WiFi). Pointless and evil. Waste of £30. An HDMI cable to a suitable laptop or Android gadget will do more than Chromecast, which can't even do 25 fps / 50fps frame rates properly. A perfectly good HDMI cable is €2, it's internally a mix of ordinary wires and Cat5e twisted pairs.
I've no idea what the Amazon streaming box does (though they want to use it to sell games and video subscription). But Roku is market leader for good reason. Lots of people do their own with a cheap fanless micro ATX or similar
and XBMC.
For Internet on HDTV screen I use a laptop or my Media PC, which has 2 x Satellite tuners (each choice of 4 satellites in Freesat and "red button"), IR remote, 2 x DVB-T (Terrestrial tuner) and HDD for scheduled recording. But since getting a Humax Freesat HD PVR (which by hidden menu can select 3 other satellites) we don't it much.
My oldest laptop does composite Analogue or VGA. The HDTV has 4 x HDMI, VGA, Composite, S-video (Y/C), SD & HD Component, SCART RGB etc. Some newer stuff here does HDMI (Wife's laptop, my Sony Z1 phone, tablet, Raspberry Pi Model B, Humax, PS3, PS4).
Smart TVs are a waste of money / features:
1) They don't update them. Lots don't work with YouTube any longer.
2) Some "spy" on you.
3) Rubbish security
4) Inflexible and less functions compared to XBMC, phone, tablet, laptop etc.