If you're happy with OpenBSD, probably any computer is good enough
Can relate, a while ago (around 2016) we bought 7 second-hand dual opteron 8439 (12 cores! no ht) desktops with 64GiB of ram in them, added pcie nvme adapter, for about ~850 EUR (including 21% vat) a piece.We have been using those systems since then and they are really amazing performers (linux and bsd, many java apps, jetbrains IDEs, etc). This is totally because of how efficient and minimal modern Linux and BSD distros can be, by the way - even with modern desktop environment like Gnome 43!Only downside is the powerdraw. They idle at 180 watts, s3 sleep is still 150 watts and on BSD idle is 240 watts! This wasn't too much of a problem before the whole energy crisis thing, because electricity was quite cheap (around 0.19cts per kwh). But with prices touching 0.80cts pet kwh, it becomes untenable quickly.We currently Wake-on-LAN these boxes only when we need them and they auto turn off after 1 hour of idle.