The mother of all resolutions, well the most popular one. Here we are at the most common used resolution for the Radeon/GeForce gaming class, 1920x1080/1200 are the most preferred monitor resolutions this year and age.
Even the GeForce GTX 660 is horribly sufficient. AMD Radeon wise well, the cards are performing really well overall. Even a Radeon HD 7850/7870 will be very suitable, but we like that 7950 Boost edition alright.
And last but not least the mac-daddy of single monitor resolutions, on a 30" 2560x1600 pixels monitor, this resolution will require a spicy graphics card as it renders over 4 Mpixels per rendered frame (!). A GeForce GTX 680 as recommendation would be valid, but again... the GTX 660 is managing just fine.
On AMDs side the Radeon HD 7900 series manage really well here. But even the 7800 would be more than suitable and usable.