I want to buy a computer which is quiet, i.e. I can leave it in my bedroom without noticing it (under normal load; I might rarely do some heavy processing, where I can accept that I would hear the fan, or on lots of HDD access, it's ok if I quietly hear the HDD; mostly very similar to my MacBook). Also, it should not consume too much energy (because it should run permanently; again similar as my MacBook). It should come in a tower where it is easy to install further disks or other hardware (unlike my MacBook). It also should have wifi.
Initially, this will mostly be a fileserver, running Linux. Maybe additionally some software like Perkeep, which needs lots of RAM (10GB or so) as far as I know. But maybe I want to run some other stuff (some scripts, maybe home automation stuff) later on it as well.
I was looking a bit around. But already for the power supply, I did not found much without an active cooler. Maybe water cooling? But as far as I know, this also has some active cooling element? I would prefer a solution which only comes with passive cooling, if something like this exists.
(Related question is here, but I don't really want a mini PC (or at least not necessarily). Preferably I also want to buy the individual components separately and configure it how I like it, at least if that is cheaper.)