The GTX560 runs cooler than the GTX 470 and uses less power. I checked that article and it never said anything about the GTX 560 running hotter or using more power. Your PSU should be enough for the GTX 560. The only caveat is that because each 12V rail is only 21AMPs you'll have to make sure that the graphics card is not on the same rail as the CPU or any other components with high power draw, otherwise that rail will get overloaded.
PCIe 2.0 cards are backwards compatible with PCIe 1.0 slots, so that shouldn't be a problem. Keep in mind though that if you were getting an AMD card then it may not be compatible because many AMD cards use PCIe 2.1, which isn't backwards compatible with PCIe 1.0. Also, as as long as the card has a 16 lane PCIe 1.0 link then the lower bandwidth won't be a bottleneck at all.
As to the question about what frame rates you'll get we need to know what games you want to be able to play. Overall the GTX 560 is capable of playing most games at 1920x1080 at high settings without issues.
GTX 560 /w Corsair 750W (60A 12v) did the trick! Fallout runs on max everything in 1920 without a hitch!
Sweet. Thanks for coming back with your results. I was thinking of the GTX 460 but for just $50 more I may as well go with the 560 Ti.
I also have a 680i MoBo that only supports PCIe 1 so I guess i'll be okay as well then. Let me know what other games you're playing now on your setup