Well I have a psu that does not have a 6 pin but it has 20Amps on 12v rail so whats the best card without use of 6 pin but i have 6 molex cables unused
A GT240 is the best video card that does not need a 6-pin connector. If the rest of your system doesn't use much power though you could probably run a 9800GT or a Radeon 4770 using a 6-pin to molex adapter without too much trouble.