Been researching the diff. & best I can find is X1100ES has a built-in DAC and X800M2 does not. Otherwise the two are identical in features. I will use the Integra AVR DAC for SACD, CD & Blue Ray (I don't plan to significantly expand this library).
Regarding streaming, Sony.com says the following 'The UBP-X800M2's playing power goes far beyond 4K UHD Blu-ray discs. You can watch, listen to, and stream almost anything you like – including most High-Definition video and High-Resolution Audio formats, and a host of popular streaming services.' If in the future I get deep in HiRes audio, there's opportunity for improvement with an external streamer/DAC.
Regarding streaming, Sony.com says the following 'The UBP-X800M2's playing power goes far beyond 4K UHD Blu-ray discs. You can watch, listen to, and stream almost anything you like – including most High-Definition video and High-Resolution Audio formats, and a host of popular streaming services.' If in the future I get deep in HiRes audio, there's opportunity for improvement with an external streamer/DAC.