With that Resolution two 690's would do fine, but make sure you get cards with LOTS of Vram!
For a dual chip card, the 690's advertise as 4GB, this is not total for the RAM needs to be mirrored in each chip, effectively you have 2GB/chip. For most games this should be fine, but at that resolution games with better textures (Crysis 2, Skyrim HD pack) You will preferably want more VRAM.
While Skyrim specifically manages VRAM terribly, I will still use this as an example. (1920x1080 1 screen)
I Own a GTX 480 with 1536MB of ram, and with an HD Texture pack installed, my ram usage is at the whole 1.5GB. Sometimes if too many textures load too fast, it crashes from a glitch breaking VRAM limit.
Other games such as Battlefield 3 hit 1350MB of ram at times, with AA disabled but otherwise run fine.