[noggin]

Kodi devs are working on mvc? But its ffmpeg based. i dont understand

Rpi not doing hd audio is a no go for me

so which hardware would be able to do hardware decode in future?

AIUI the Pi / Pi 2 version of Kodi is now able to use the internal Kodi player implemented on the PI to playback MKVs with MVC conten, and output this at full frame-packed 3D resolution, by shifting the MVC decode to the hardware decoder that the Pi / Pi 2 GPU/VPU contains. ISO support isn't there yet, presumably because ffmpeg's demux for MPEG2 transport streams - which is the wrapper that Blu-ray ISO and Folder content is wrapped in - doesn't bother with MVC streams as they aren't currently supported for decode, but there is MKV demux support?

Other 3D capable hardware (Intel/nVidia/AMD under Windows, Android players etc.) use external players to implement 3D MVC decode AIUI?

Pi 2 will do Dolby True HD decoded losslessly to PCM (though not 5.1 at 192kHz) in a manner pretty much the same as your amp would.

If you are offline converting ISO to MKV you could also offline convert DTS-HD to FLAC or PCM at the same time if you have the right (not open source) software.