the Sabbertooth gen 3 has pci-e 3.0 yes. do you realy need it... no.
there arent any games who use the full bandwidth of pci-e 2.0 yet. its just an higher number.
maybe in the future there will be games wo gonne take the full bandwith of pci-e 2.0.
till the time games realy getting bottlenecked with pci-e 2.0 then youre gpu is so outdated allready.
so yea its just more an hype then a must have.
notice that on most pci-3.0 boards only one slot is running 32gb/s the rest of the slots mostly 16gb/s and 8 gb/s so also in crossfire or sli i dont see why it should be better..
PCI-e versions don't really matter all that much. I just upgraded from a motherboard with 1.1 to a 2.0 board and my GTX 560 Ti performs pretty much exactly the same.