Back on topic, a GTX 970 is over the top for 1920x1080/2560x1080 for a single year and I don't think they're available in a single slot design that's mostly required for the most compact Mini ITX cases.
IIRC the fastest single slot card is the GTX 750ti which should be sufficient for what you want. There are even a couple of half height versions around, although they are dual slot.