If you're planning to run 7970 crossfire then you'll have enough power to run a high res 27/30" or a 120hz monitor.
From my experience, if you predominantly play fast pace games like Battlefield 3 or racing type games, go for the 120hz monitor. Otherwise, I'd look at the U2711 or ZR2740W.
120hz is smoother than 60hz if you have the video card(s) to push 120 fps. However, I've tried it and it didn't seem to make me any better or enjoy the game any more than with 60hz. I'd go with an IPS panel instead of a 120hz panel.
A forum community dedicated to overclocking enthusiasts and testing the limits of computing. Come join the discussion about computing, builds, collections, displays, models, styles, scales, specifications, reviews, accessories, classifieds, and more!