I live in an environment so noisy that it's certainly a significant contributor to my long-term hearing loss. Some of you surely select machines based on how quiet they run, though. It's hard to get a lot quieter than completely silent, as is the case with passively-cooled PCs like Zotac's Zbox C series. The latest model in the line-up is the Zbox CI329 nano powered by a quad-core Gemini Lake CPU.
The specific chip in question is the Celeron N4100. That's a four-core, four-thread chip that runs at 1.1 GHz but will briefly burst up to 2.4 GHz when necessary. Even including its built-in UHD Graphics 600, it only has a 6-W TDP. Taking that power draw into account, it seems unlikely that the machine's large heatsink will even get warm as long as there's any air flowing past it at all.
The CI329 Nano has two DDR4 SO-DIMM slots and one 2.5" SATA drive bay—and that's it for external expansion. You can leave 8-GB SO-DIMMs in the shop, too—Intel says the machine will only accept 8 GB of memory in total. Said IGP can power three displays simultaneously using the CI329's HDMI 2.0a, DisplayPort 1.2, and VGA connectors.
That amount of connectivity is pretty good for a machine barely 2.3" tall (5.8 cm) with a footprint that's just 5" square (12.7 cm). Other external connections on the CI329 Nano include four USB 3.0 ports (one of them Type-C), a USB 2.0 port, 3.5-mm headphone and microphone jacks, and dual Gigabit Ethernet connections. Thanks to that last listing, I'm already eyeing one of these little boxes as a replacement pfSense machine. If you're interested too, keep an eye out. Zotac says the machine is out, so it should hit store shelves soon.