The 680i chipset is now old standard which is why its cheap.
Why the 64bit version of Vista? (In fact, why Vista?? Direct x10?)
You will need 64 bit drivers for all your peripherals and hardware. make sure you can get them.
You need to check the PSU to make sure its capable of running 8800GTs (never mind in SLI) They require a lot of Amps.