I have recently bought my new graphic card. I tried to buy a cheaper high-end card, which I could use to play the latest released games. I wanted this one, because it offers a great results. I am going to eplain you why. It is because the graphic card has a 320-bit bus, so the data are transfered pretty fast between the components on the graphic card. I conclusion with other graphic cards - I dont recommend you to buy that 640MB version, if you dont have money to waste. And in conclusion with Radeon I think, that Radeon is not good enought right now to make the gamers satisfied. It runs great with my configuration, which is an old AMD Athlon 3000+ OC, 1, 5GB RAM DDR and MB ASUS A8n-SLI Deluxe. I played games like Settlers IV and Half-Life 2 Episode Two on it and it runs without any problems, even if I set graphics to maximum.
I also recommend you to buy this card after some new release from GeForce, or at least after the Chrismas time, because the card is overvalued right now.