Question is too vague.... Corsair makes some good PSUs, some great PUS and a lot of crappy PSUs.... The specific model number would be required to give an accurate answer.
Need the model of the PSU and more importantly what it's going to be used with - you are talking a 600 and a 400, you have have the greatest 400 in the world but if it doesn't have enough wattage for your rig, it's going to be worthless