1080s are going to go for about the same or cheaper than another 980ti. Combine that with the fact that not all games will support SLI, that is a lot of money for a questionable return. But comparing the two single cards, the 1080 will outperform in everyway, and is more power efficient. Every game will be better with a 1080 vs single 980ti,but not all games will perform better with SLI. I would recommend selling and picking up an AIB/aftermarket 1080 when they come out. I hear the founder's edition has power throttling issues, and ASUS, Gigabyte and the others have already teased their STRIX/WINDFORCE versions - shouldn't be too long. Hope it helps!