I box fine with 8GB of RAM with an amd phenom 1055t (3.4Ghz). With windows 7 and 5 wow's running I'm at 4.5GB of used RAM. For the rest of the comparison I have a radeon 4890 1GB video card and an intel x25m ssd (80gb).

My main client is on ultra settings with everyone else on low (except for draw distance). I get 60FPS most times on my main (except in Dalaran).