I just saw a video playing it on very high settings with 2xSMAA running around 25-30 at 1080. Your card can run Battlefield 4 on high settings at 900p at a solid 60fps so I honestly don't see why Crysis 3 shouldn't run on medium at your desired resolution.
By the way when I bought my GTX660 I was told by many, many people on youtube and in forums that it was a terrible card and that I wouldn't be able to run anything. I honestly didn't find many games that couldn't run at near ultra. Metro Last Light and Crysis 3 gave it trouble but that was at 1080 on ultra settings. PC gamers tend to exaggerate. So in my opinion you should be good.
Benchmark of Battlefield 4 running perfectly. It starts to struggle at 1080...