For silence just make sure the chipset doesn't have a fan.
I think there are only two socket 939 boards w/o integrated video. One is a Foxconn using the Nforce4 chipset. It is almost not overclockable IIRC. The other board is an eVGA using the Nforce4 SLI chipset, and yes this mATX board does SLI. :Q Not 100% sure but I think this board is moderately overclockable.
I can't think of any motherboards made in the past couple of years without onboard sound, except for boards like the DFI LANPARTY with the daughtercard.
I'd say to ignore onboard sound and video because you can just disable them and run a PCI sound card and PCI-E video card anyways.
DFI makes a decent mATX board using the ATI IGP chipset. EPoX makes a decent one using the Geforce6100 chipset. Biostar makes a decent one using that chipset also... but make sure you get the Tforce version. The Asus mATX board using the Geforce6150 seems popular, but it almost doesn't overclock.