It would appear his preliminary choice is the Zotac 980 Ti but before pulling the trigger, OP wants to consider other options.
Twin 970s is about 20% faster than a 980 Ti when both are overclocked "bawlz to the wall". To do the 970s tho you will need to bump the PSU size up from a 650 to a 750 watter. In many cases, At "out of the box" settings, the advantage is a bit wider because nVidia has artificially capped the performance so as not to have it too close to the 980. The 980n Ti is a great overclocker with all of the major non-reference designs getting 26 to 31% OCs. The 980 Ti has a max temp of 92C and throttling kicks in at 85C giving you a nice 7C cushion.
The 970 which has a max time of 98C, you would expect it to start...