Thats what it seems like we're agreeing on so far.
However, there's a few things mentioned which is just not true. For example, the second graphics card being used for physics calculations. That is not true as far as I know. It is possible to get a graphics card to do physics calculations, but when hooked up in SLI, it doesn't do so. Maybe a little...
Also the fact that SLI requires two PCIe x16 slots. This is more or less bull. Graphics cards today, even the top end 8800gtx, do not utilize the full potential of a PCIe x8, much less the x16. In fact, with the dongle, you just need a PCIe x16, and a PCIe x1 (with the size of a x16 slot), and it should perform close to what two true PCIe x16 slots would give you. There are some benchmarks out there showing that it is true x16 will give you higher performance, but you're talking below 5%, typically 1% improvements in benchmark points.
Also, SLI does give performance gains, but as mentioned, not a double in performance. You'd be lucky with 50% improvement, and I think its normal to get between 25-35% improvement.
IMO, if you're not getting an SLI system of the top end card in the market at time of purchase, there's no need for it. Some say you might want to add in a second card later, but if its much later, you're better off getting a whole new card to replace the old one (due to advances in technology). Or you're cheap, and just want to spend a few bux for a small improvement in performance, in which case, you'd probably be lacking in some other components in your computer.
