Hi guys.
 
I am planning on buying a new box based on nvidia geforce 9600 gt. in the future (when 9600 gt prices lowered), i plan to purchase another 9600 gt for sli setup.  
 
problem is, the cheapest sli pcie2 mb are very expensive for me (750i). does pcie1 bottle neck 9600gt? or it bottleneck only when in sli setup?
 
ive tried google for analytical analysis but found nothing that helps(the nearest one are for 8xxx series).
 
Thank you guys.

I am not an expert, but I don't think that there will be any bottleneck with your pci-e slot.  
I think that the pci-e bus haven't reached the max yet and that you will be ok with a pci-e2 card in a pci-e1 slot.
I hope this helps.

It's more hype right now than actual performance. Just like when they went from 8x to 16x, from AGP to PCIe. In the future it will be helpful but I haven't seen any benchmarks that would make me think its worth the money right now.

It's okay to run PCI-E 2 cards in PCI-E 1.1/1.0.
There's not much difference, at least for the 9600gt (or any recent PCI-E 2 cards).

9600gt isn't nearly powerful enough for the bus bandwidth to be a bottleneck. There's no difference.