Project definition is going faster than I thought:
Raspberry Pi4 2GB, as headless units don't need the extra memory. If it does, somewhere in the future, I'll upgrade the entire unit to the RPi 5 our 6 for about the same price premium I'd have to pay now.
Original Raspberry 15W PSU;
Small 1,3" 128x64 oled display
Heat sinks from the scrap pile (I have a lot with a choice of size and colours
);
A ply wood box (with some leftover pieces from previous projects), to add a touch of class on top of the DAC (Topping E30) and near the Prima Luna;
iomega HDD 500GB (USB 2.0 and a little bit noisy because of the 7200rpm; it also requires it's own 12V PSU). If I find it inadequate, I can sreplace it with a newer unit (WD MyPassport USB 3.0).
32GB micro sd for the OS (I think I'll upgrade my phone 32GB to a 64GB card and then format and reuse the 32 in the RPi)
Cables I'll use and reuse from the tons I have at home...
I just miss a huge thing: which OS and software for streaming. I'm lost in all the distributions and options (Volumio, Rune, Roon, Plex...). I'm not a software expert. I can run an installation and do some parametrization but not something too big.