Rayman, what type of dual monitoring do you need? 2x Monitor or would Monitor/TV be enough? Do you need independent screen resolutions and refresh rates?
What do you mean by "decent 3d graphics"? Gaming? BP6 compatible CPUs will be too slow for recent games (unless you plan to use some Tualatin-adaptor-wizardry). A fast video card won´t help much. UT will be nice, UT2003 will be slow. Single player and heavily cpu-dependent games like MOHAA or U2 will be very slow.
BP6, RU BIOS, XP SP3, ACPI, 2x366@523(1,95V), Pentalpha HS + 1x 12cm fan @5V, 768MB, Powercolor Geforce 3, RTL8139D NIC, Terratec EWS64L, Samsung M40 80GB (2,5''), LiteOn CDRW