Thank you for the detailed reply!
First of all I will only go for hi-res streaming via Qobuz.
The Core wasn‘t my first choice. I think a third party option is better in this case.
RCA or digital is the question.. I think the most usable option is RCA or digital to the BS3. This way everything stay the same. And I don’t need any cables in the living room.
Used equipment would be an option here! I‘ll take a closer look on the Auralic stuff. I‘m willing to spend 1.000€ on this project. Thank you so far.
I need to say I am not „scared“ to pay the price of usability loss if better sound is what I get.