I went from a MSI gtx 570 1,2gb to a new gigabyte gtx 970 g1 4gb
Running a 2700k @ 4,6ghz
Dell U3014 2560x1600
With gtx 570:
Prepar3d v2.0 to 2.2... I had to go down the resolution to 1920x1200 mid level in graphics setup
Prepar3d v2.3-2.4 I could use 2560x1600 with pretty decent results
Now, with gtx970, Prepar is like an other simulator. I use prepar3d fps limiter to 30. It is rock solid at 30fps with FsGlobal Ultimate + FTX global + FTX vector + FTX OpenLC Europe with most detail at max setting.
Huge improvement from gtx 570 to 970.
2560x1600 is quite demanding resolution.