How about new technology?
What if SLI was out a few years ago, u had lets say a 9800Pro, u bought another one now...
the 6800U has SM3 already, so in fact factoring in that performance gain... it would be faster as newer games are using it now, albiet only partially.
IF i was a hardcore enthusiast, which i am, sorta... i would go for the new tech over pure raw power, as thats what i want for my new games...
In the end, the new tech will give performance advantages to the SLI configuration. Just like SM3.
Or perhaps a more up to date example. u buy a 6800U, then u buy another 6800U over a year away, UE3 is out, using SM3, but even with both ur cards running, it would barely play it, maybe twice as many frame rates than the UE3 demo with a highly overclocked 6800. But the new cards out on the block CAN run UE3 easily, with all the added extra features that its ladened with.
IMO i would go always for the newest and best card, but i wouldnt have SLI as down the line i would still have to cater for the lowest common denominator, which happens to be the card already in the PCI-E slot, so there is no updating of your GPU config, all ur doing is overclocking it by buying another card.
But my speculation and opinions are early as there are no benchmarks nor are there any news on it, so i will keep all my other judgements back until then, when we can test it out, on older and newer cards.
But i have seen that SLI will be coming in October this year, is this true?