order an 8800 off of newegg, its WAY cheaper. they sell 8600GT's for like 200$ (bestbuy)
anyways, crysis wont really max it out, it will evenly spread the load off all of the cores, but you wont NEED the 4, probably just 2 of them.
no games will use them, but if you do lots of video encoding it will help a lot. also 3D rendering of big objects will be sped up dramatically.
CSS is single threaded, and im pretty sure age of empires is too.