I'm running a gig of ram and a Geforce 6800GS AGP, and I'm not worried about running the game. Of course, I'm decently overclocked on most of my hardware. Geforce 6800 series is the minimum, because it supports pixel shader 3.0. Radeon supports it now too, but they took a little longer thus the cards that support it are a tad more expensive than the 6800s. 6800 Ultra is nice, it's got 16 pipelines and probably is pretty affordable now. My 6800 GS is AGP and only has 12 pipelines (there's a way to try to unlock it to a quad but my card wouldn't have it), but I've got it running fast in other ways.
I run both Oblivion and Titan Quest at 1280 by 1024 with no lag (Oblivion I do have a lot of performance tweaks, Titan Quest the graphics are maxxed out with no issues). I don't expect to run AoC on max settings, but I figure, if I could run EQ2 I shouldn't have any issues with AoC assuming it's properly optimized.
