I know that we are not suppose to post unless we intend to buy but apart from 6990, 690 and 7990 a 540w pus should be able to handle any graphics card as long as it is a good quality psu
Coolermasters silentM series they get good reviews but not great...if it was going into my main rig that runs a corsair psu i wouldn't worry but with a good psu not a great one i like to air on the side of caution and go by Nvidia's stats sheet
Again I am sorry for off topic post but you should really know that the 560ti actually has a higher power consumption than the 670 and is about equal to the 680