The soekris is even easier to setup as it simply works with enabled keyboard and video and you don't have to swap kernels (though it doesn't have these components, the bios works around it pretty well). Just install pfsense from cdrom to your media in a system that supports booting from cdrom. Leave the nics assigned as sis and move the media to the soekris after the install has finished. You should be able to access the gui right away after booting up form the default lan interface. Enabling serial console at system>advanced is recommended. We installed a 2,5" hdd in my notebook this way and mounted it to bills soekris 4801 during the hackathon.