AMD 390x= GTX 980. (I'd go with 390x because all you need is a good cooler and it's also cheaper.)
AMD Fury X= GTX 980 Ti (I'd go with the Fury X because it displays more fps at such a small size.)
if on sale the the gtx 980 even though id recommend getting the 980 ti since its soooooo awesoem
but yeah if ur on a budget the 970 is perfect its overclocking capabilities can get faster then the normal 980