I run 3 Pi 3B+ in my home. The most interesting setup (kitchen) is Allo Boss HAT with twin PSU; Ifi for Pi and LPS for Boss. although they only feed into analog input on a modest Denon M40DAB & Wharfedale Diamond 10.1 the result is so clean, clear and revealing of detail and musical subtleties.
Part of this setup I would never be without is a metal cased Switch TP-Link TL-SG105S (connected between my home network and Pi using Cat7 cable) This appears to buffer the Pi from network interreference.
The addition of this switch has to be heard to be believed; Stereo stage placement, detail, clarity and smoother sound are immediately evident. anybody with a Pi/Dac should try this at £11 its so very worthwhile.
Not wanting to use fans i have only added small adhesive heat sinks to the Pi’s but have never been aware of undue heat.I have never tried a Pi4.
I listen to Nas based FLAC files or stream FLAC from Radio Paradise. Having a Strong front end allows a modest amp/LS to shine. The PSU’s and switch are only present based on the perceived improvements they bring.