DFI Lanparty Ultra-D motherboard. You can modify the Northbridge to make it a SLI board for cheaper, if you ever wish to do so later on.
AMD Opteron 165 Dual Core Socket 939 Processor (Double cache of x2 CPUs FTW)
2GB Dual Channel Memory. There are good and bad. Find some links, PM me… i’ll tell you yes/no 
Video Card… hmmm… with that price range, you can probably go X850 for around $200, or something a little nicer for around $300 (maybe a 7800 of some type). Make sure its a 256-bit video card, at least 256MB GDDR3 RAM, PCI-E x16, more than 12 pipelines is always nice.
People primarily run two high-end video cards if they’re gonna go SLI. The price vs. performance isn’t there, so you’ll get more performance from a $300 video card than you would with, say, two $200 ones running SLI.
I’d steer clear of the SLI with a budget of only $1200. Get a decent $200-$300 card.