Amazon Prime won`t work in 1080p. Get an Amazon Stick for that if you need it.
I'm getting good results now with an overclocked S912 GPU and new GPU drivers and tweaks that went into my S912 LE Krypton Subtitles fix release.
For example I can now playback 1080p 11Mbps 10bit H264 aka Hi10P Anime - that uses CPU software decoding. This is the same software decoding that AML Kodi Leia uses with the Netflix Addon. I've done further testing with other 1080p H264 CPU software decoded content and it plays back fine.
I now strongly suspect 1080p Netflix and 1080p Amazon Video - Kodi Leia - H264 streaming may work on a AML S912 when using software decoding.