probably a better deal to get 970sli though even 1 will do great at 1080p.. for 970sli i would say go for 1440p for some great quality and frame rates.. can of course go higher just depends on the standard you have
My personal opinion on 980 is that unless it goes down to $425 or so, it's not worth it over a 970. At the current price even SLI 970 has better bang for th buck than a single 980.
when people say 970 is better for price and blablabla, they are actually right, 970 is right on the 980's heels in every aspect, not worth the extra money for 980... especially this series of cards, 970 is just too good