I feel like it may be a wise choice to go for the 980 now and SLI it later this year, maybe Christmas time. I'm going to order the Strix and test it, if it's not much better than I have no idea lol.
Also it would appear the Strix 980 doesn't use just one 8 pin cable, that is the 970. http://www.bit-tech.net/hardware/graphics/2014/10/08/asus-gtx-980-strix-review/1Look at the 2nd picture here.