Most people I know have said that SLI is a waste of time and money because very few game support it properly, you are better off saving the money you would spend on the second card and replacing the first card with it at a later date.
As for AMD Vs Intel. Yes, the chip you have chosen runs at 3.2GHz but clock for clock the Intel chips are better, the price difference is worth it (look up some benchmarks if you don't believe me). Most people building gaming PC's at the moment seem to be getting an Intel Q6600 (Make sure it is the G0 stepping when you buy it, it will run much cooler) and a 512MB NVidia 8800GT.

