Thats true only CS5 will take more advantage of a video cards processing power. As for the 700W PSU idea, thats only for someone running two gaming video cards.
As for the 128/256/512 bit memory buses, its performance actually changes with each advance in the overall design of the gpu. So you can't say 256 is better than 128, you have to read the reviews to figure which is best.
Take a look at This Review, there you find the power consumption and other performance tests for the core 860 cpu. They are using the GTX280 video card (high power gaming card), the system uses at idle 91W, full load 185W. Then they overclocked the snot out of the system, it then used 146W at idle and 305W at full load. So as you can see even the 400W PSU will work fine, a lot of us would also rather 500-600W as well but its not necessary.
Actually just to note, they didn't really stress the video card when doing the load test, it was more of a CPU load test, so under higher gaming it would have easily used another ~100W. But again your not going to get a high power gaming card.