I have a 1080p monitor and use DSR to play at 1440p. Dont have any issues. What do you see when you use DSR? Are you using 3 monitors or just 1? Did you enable DSR in the Nvidia control panel and choose the proper multiplier to get a higher res? Once that is set in the NV CP, you can choose any custom resolution in game and select it, and it will automatically fit your monitor.