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Thank you for bringing this to my attention.
Since the PCI Express 3.0 is a standard, it means that there isn't any difference in compatibility/performance on the processors that support it, the Intel® Xeon® Processor E5-2687W will perform the same as the Intel® Xeon® Processor E5-2697 v3.
To know if a processor supports PCIe 3.0 you can check the following link:
ark.intel.com > Processors > Intel® Xeon® Processors > Choose the Family > Choose the Processor > Expansion Options > PCI Express Revision.
As for the SLI support, it depends on the motherboard and the graphics cards being used.
I hope this information helps.