I have an Intel SAI2 setup that my wife uses daily. Its got two 1.4 GHz-512 KB pieces in it. It is a pretty solid board, and can be had for the reasonable price of $35 these days. The 64-bit/66-MHz PCI-X slots are a nice addition which can be used for high bandwidth SCSI/SATA or Gigabit ethernet cards.
The missing AGP graphics is the main drawback, but it does work fine with a NV 6200 256 or 512 MB. The only other issue with using a graphics card with so much RAM is it limits the amount of system RAM addressable on the system board, which is normally 4 GB (with the onboard graphics), but with the NV 6200 installed, the addressable limit drops to ~2.7 MB, which is not a big deal though.
I had hoped that the odd-ball Matrox Parhelia 256 PCI-x card would have worked in the PCI-X slot, but there seems to be a hardware conflict that neither Intel, nor Matrox want to address.
Before the Intel SAI2, I had another dualie, an ASUS CUV4X-DLS (4X AGP), which wasn't nearly as stable and eventually gave way.
Plan your life wisely, you'll be dead before you know it.