looking for advice on a low power (quiet) mobo and cpu?

I'm putting together a cheap little system to run as a NAS solution for everyone in the house (just using windows workgroup and file sharing settings) along with being hooked up to a 50' 1080HD plasma and stereo to play dvd's and cd respectivley.

I aim to use a half decent gpu to deal with 1080 graphics (as I plan to replace the dvd with bluray eventually) and the majority of storage needs (bar the OS and program files) will be dealt with by external usb powered HDD's

I will need a decent number of usb ports though to attach the hdd's, wireless trackball, keyboard, etc.

This will be my first build by the way so go easy peeps, I'm still learning. Thanks