Intel BOXDG965WHMKR LGA 775 Intel G965 Express ATX Intel Motherboard - Retail - $116.99
2GB Worth of Kingston RAM, certified to work with said motherboard - $74
But this could work for me almost as much as for you. I won't need a video card right away (since I don't do intense gaming), I have RAM upgrade options, and it's under $400. Also, there are several confirmed Linux sightings that don't involve binary drivers. Color me . . . fuligin.
Holy crap do I need to go to sleep.