Wait did we all miss something? You are doing dual processors? You can't with AMD64 4000+ or FX series, only Opterons. That is what I am doing. You cannot, repeat, cannot do dual AMD64 processors except for Opterons. And with all that money, do what I am doing. Get a TYAN dual Opteron board, and two dual phase core Opterons. That will scream, and make sure the board is the SLi Thunder from Tyan. Then you will have dual graphics cards in SLi setup. If you are planning a dual MOBO setup, forget it, it has more problems then a Beowolf Cluster, trust me, tried it before....
Anywho, if you were going to try a dual CPU setup with processors you listed, I sure wouldn't. I am building a PC that would eat that for lunch, and costs almost 1,500 less.......... Whatever you want is your choice, but dual FX's is non existent. Their onboard memory controller won't allow for it, same with normal AMD64 series. Only Opterons with dual core and Memory controller will work. Nice video card, but with that type of money, go the route I am going in January, get a PCI Express TYAN Thunder SLi board, and do dual 6800Ultra Extreme Edition PCIe cards, and dual Opterons. Can't wait, you are the first person to do kinda what I am doing, GO YOU!
Also, TYAN Thunder SLi allows for up to 16GB of RAM, I am doing 8GBs in mine; especially if you do Adobe PhotoshopCS, etc, the more ram the better!