You won't find any dual a64 board now, and i doubt they will ever be made for dual processors, however there is the opteron line which will give you near the same performance, but they are a bit more pricey, and require more expensive parts. For opteron's, you have to make sure you get processors that are dual compatible, i think the one hundred series is for single processors only, the two hundred can be used in duals, and then the 8 hundred line can have up to 8, but i may be wrong with those. They come in speeds of 1.4ghz-2.2ghz corresponding with model numbers x40-x48.AMD opteron specs
Heres the boards newegg has:Dual 940 boards
Another option would be athlon mp, don't know how much of a necessity 64 bit is to you, but you could look for a dual socket A(462) setup.Socket A boards
hope this helps some at least.
A64 3200+ @ 2.1ghz(not pushing it)
MSI K8T Neo
Mushkin pc3500 512 x 2
video card...dont ask...waiting on new ones