So I have a 550ti and the performance is horrible on some games, but on others it does fine. i dont know what the problem could be. i tried redownloading the games that wouldnt work from steam and that didnt do anything, and i dont think its the card, because i put it in a friends computer and it worked fine. what i think it might be is the PSU. My 12v rail is rated at 14 amps and the card requires 24 amps. Could this be the problem? it plays metro 2033 great, but i cant play saints row the third at lowest settings. So do i need to get a new psu, or is it a different problem?