Passive cooling is the holy grail for folks looking to build quiet PCs. It's particularly important for home-theater rigs, and MSI has a new motherboard that looks like a good fit for that mission. The C847MS-E33 takes an ultra-low-voltage Celeron processor and NM70 chipset from Intel's catalog of notebook parts and puts them on a microATX board. Since the CPU has a thermal envelope of only 17W, it can be cooled with an unassuming-looking passive heatsink.
Granted, the Celeron isn't the fastest chip on the block. This Sandy Bridge-based duallie is clocked at 1.1GHz and features 2MB of L3 cache. The integrated Intel graphics should be sufficient for HD video playback, though, and there's an HDMI output to connect to your home theater. The board also includes two flavors of S/PDIF digital audio output. It lacks USB 3.0 support, though, and it's limited to one 6Gbps SATA port and three 3Gbps ones.
MSI includes a Gigabit Ethernet controller and provides plenty of expansion slots. In addition to a PCI Express x16 slot, the board serves up one x1 slot and two old-school PCI slots. Solid-state capacitors are used throughout, and you even get a UEFI firmware.
The C847MS-E33 doesn't appear to be selling online just yet, but I'd expect it to be inexpensive. People are only going to pay so much for a Celeron that barely eclipses the gigahertz mark. That said, it is worth spending a little bit extra to get a real CPU instead of settling for an Atom-based system. Kudos to MSI for coming up with a passively cooled motherboard that doesn't scrape the absolute bottom of the CPU barrel. And thanks to FanlessTech for the tip.