Like most of the age series, the settings are adjustable to scale down to lower end systems. They are still working on the game, and most optimizations will come at the very end, so it is difficult to pin down specs at this point.
To run this at full rez and quality settings, you will need a beefy processor and a top of the line video card. As with any of the age series, RAM is very important especially for multiplayer 3v3 games. CPU is always important because as more units get added, late in a multiplayer game, or early in a DM game : ), the pathing for the units gets calculated by the CPU, which is the reason for most slowdown. The graphics are very advanced, and take full advantage of all the newest technologies that the very highest end cards offer.
In short, if you have a top of the line gaming rig, it will look great, but it will take next gen parts to push it to its fullest potential.