+1! -- I use Optiplexes in my homelab for client/misc/fw duty, and I have a pair of Supermicro mini servers with Xeon-D chips for slightly heavier stuff. Both bulletproof and small/innocuous/inexpensive to run.

I keep wanting to upgrade to something shiny or attempt to consolidate since my Dells are on some hilariously old chips (4th gen LTS "T" series i7s) but man they just keep chugging along, it's hard to justify.