I wonder 5.1 AV system

[da2001]

The cheapest option would be a mediaplayer with Kodi (v17 performs the decoding rather well and you can perform Some kind of DSP) and a miniDSP nanoavr HDA afterwards with A/D converters for each channel.

This one is an interesting solution but how about the SQ when converting A to D once more after D/A?

i´ve spend a lot of time to found a solution for this. As long as devialet cant reduce the input lag of 160-250ms, you wont have a good result.
i tried multiple setups of avr receivers and delay correction devices, but nothing helped me out. 
So i contacted devialet and they told me "Our engineers are actually working constantly to improve our user's experience, update after update"
I think this is the default answer for every email which cant be answered satisfiable

so dont be disappointed if there will be no solution with the actual hardware..