the gtx970 is plenty for extreme modded skryim at 1440p. as long as you "mod" the game correctly you will have no problems.
skyrim modding is sort of an art, you cannot just toss a bunch of mods together and expect skyrim to work correctly. you should really use mod packs or find lists of known mods from reputable modders. otherwise all mods need to be bashed, tagged, cleaned, and ordered before you can start a new game/new save file.... otherwise you run the almost inevitable risk of killing a save game file rending the game useless. figure on about a 4 hour learning curve to understanding skyrim and modding the programs needed and another 4 hours of computer work actually using those programs, not including mod download times.