Impact a 2560x1440 monitor will have on performance?

[caq]

x64
GeForce GTX 560 Ti
Intel Core i5-2400S CPU @ 2.5 ghz
8.00 GB RAM
Windows 8.1 Pro

I am looking to buy a 2560x1440 monitor, I am wondering what kind of impact it will have in performance?

 

[coregamer]

expect fps drops anywhere from around 10-20(30max) fps if you are coming from 1080p