I was shopping for video cards on newegg todat and noticed that the core and memory clock on a 7600 GT are higher than my 7800 GT. The one I was looking at was the XFX model and it had 580/1500 vs my 7800 GT which is 470/1100????? If the clock speeds are faster on the 7600 why is it called 7600 which is a lower number? I thought when newer and faster cards came out the model number went up..like 7800 to 7900? What am I missing?