The GTX 260 or HD 4870 1GB, they are the minimum for Enthusiast settings, especially on high resolutions. What kills performance in Crysis isn't AA or AF like many think, but the screen resolution, with high quality LCD's becoming more popular since the past year or two, being more affordable, most gamers want to play at their LCD's native resolution. I myself have an LCD but as surprising as it may seem I mostly use it for Photoshoping and watching movies, I actually switch the video plug on my next desk on which my flat CRT is and I play Crysis at 1280x1024, and all of a sudden I get 50FPS in most areas, with 2xAA and 4xAF. I'll get a GTX 285 next month, but I won't change my reflex of gaming on one resolution and doing other activities on higher resolutions, to me gaming doesn't require high resolutions, I prefer having AF and some AA to do the job, it saves performance, and it refrains me from buying new GPU's each years impulsively, because my LCD's resolution is the sole responsible for performance drops in the latest games.
I know lots of people will disagree, but when you're used to play under a specific resolution for years you don't really want to change in an instant. The day when a single GPU won't get choked by pretty much any resolutions changes then I will play my games solely on LCD's, but that may be something that won't happen until a couple of years if not a decade from now. At the moment high resolutions are still the main reason why we're getting such GPU's, and SLi, and CrossFire, and cards with 1GB of RAM, and X2 solutions, if people look at most PC games they're almost all console ports with low and small textures and polygon counts (Fallout 3 being the most recent example), there's no way such graphics require a GTX 295... but play with such textures on 1900x1200 and all of a sudden even if the textures are only 512x512 if you add 4xAA and 16xAF to that then you suddenly wonder why those "ugly" textures are choking your $600 card. That's how I see it anyway, but I'm probably part of the minority.