If you go with 120hz/3D gaming monitor, go with what you chose, not the Samsung. Samsungs don't work with 3D Vision 2, and I see a lot of reviews from people on Newegg who were very disappointed with those Samsung monitors in 3D, saying they were very dark, unlike the Acer in my signature, and that ASUS has lightboost that is even brighter yet.
The Samsung is good if you have an AMD graphics setup.
pros: you can view 1080p footage within an editor window while retaining space for toolbars, greater sharpness due to higher pixel density when viewing native resolution content, high resolution meshes well with all types of design work, games will look sharper than 1080p provided they are rendered at this native resolution
cons: viewing fullscreen 1080p is less crisp than on a native 1080p panel, gaming on a higher resolution panel requires a higher end system than 1080p would, no 1080p 3d.
pros: view 1080 content better, 3d, smoother display
cons: stuck with a crappy tn panel, less crisp
ideally 2560x1440 unless you want to view 1080p content as best as you can, dont want to fork out for a new video card a little sooner than you would on a 1080p system or if 3d matters alot to you.
The only pro for 120hz (I think) is potentially smoother feeling game play and general usage. Other than that, I think 2560x1440 takes the cake in all aspects especially considering you have a 690. I think it would be a waste of graphics power if you didn't get a 2560x1440. Heck, if you wanted (and depending on where you live), get a 120hz and a 2560x1440. Take a look at this monitor offered by Microcenter.