470's will give better performance, especially at 2560x1600, but they are noisy underload.
460's would be enough for 1080p and they will be a lot quieter.
CPU bottlenecks with an i7 system are kind of misleading. The i7 will give enough power for almost any game to reach 60 FPS. 60FPS is all that is needed to max out the hz of most displays. If your CPU is bottlenecking, all that means is you could have higher FPS than most monitors would be able to display, so it's pointless to worry about.
The monitor is the determining factor here. If you have a high resolution, you need more GPU power. If you get a resolution of 2560x1600, you will need the extra power of the 470's (or higher) as well as the video ram of the 470's or more to allow you to turn up the settings.
Personally, I'd get a single 580 for the 1920x1080 display, and if you get the 2560x1600, I'd get two 470's or better. And if you went with ATI, I'd make sure what ever cards you go with have more than 1GB of v-ram each if you go for the 2560x1600 display.