I agree with that analysis, however as I make machinima in SL at very high settings (ultra), resolutions of 1600x1200, some SLi configurations have their advantages. If you compare the various core/ram settings of the various nVidia range, given that I use overclocked and not 'domestic' versions, the 7 and 8 series can be more powerful. I run dual 8800GT overclocked GC's, which negate me wanting to spend anymore money for the foresseable future, hence my comment ONLY lol..
Well, obviously It's not easy to upgrade a pair of overclocked 8800GTs.
Still, the 9600GT is a high-end GC for the price of a mid-end card. - especially after tests proved that the 9600GT has huge overclock potential. The new manufacturing technologies (brand new G94 GPU core compared to the older G92 of the 8800GT), reduced consumption, and high-end speed altogether for a price of 160$ - anyone looking to buy a GC nowadays should check it out.