the pin converter will be fully compatible with the board as will the power supply the only problem is that it might not supply enough power, the reason being is that the extra 4 pins are drawing power from 4 of the current 20 pins, the extra 4 pins is purley for pcie requireing more power in the future, at the moment it is allright, if you are going to use SLI and have two graphics cards then you might need a more powerfull power supply then you curently have...
what are you amps on your 12v rail