16xAA with quake4? Come on. It's an old game but it's not that old. It's a FPS you don't need that much AA to begin with.
Yeah, but "need" and "want" are different terms.
My X1950XTX is all I "need" to play it.
That 9800 GTX+ might fit the bill perfectly. It's on par with the 4850 and allows the better AF and soft particles. Sure, it probably won't be able to handle xS modes in some of the games I play, but neither could the GTX 260.