I've already got GTX 580s in SLI but I'm thinking about playing around with a third. I'm curious what type of performance differences there might be between the z68 with nf200 (like the ASUS Maximus IV Extreme-Z) and the new x79 chipset with 40 PCI-E lanes. Similarly if I planned to go tri-sli keplers later what type of differences would the two have?