What power supply will I need for my computer?

So i'm building a gaming computer and need to know if i'll need to upgrade my power supply which is currently 400W. The parts I'm going to be getting are the AMD Phenom 2 3.4GHz for my CPU, Nvidia GeForce GTX 650 for GPU, the MSI 970A-G46 AM3+ AMD for the mobo and Corsair 4x2 GB RAM which I don't... show more So i'm building a gaming computer and need to know if i'll need to upgrade my power supply which is currently 400W. The parts I'm going to be getting are the AMD Phenom 2 3.4GHz for my CPU, Nvidia GeForce GTX 650 for GPU, the MSI 970A-G46 AM3+ AMD for the mobo and Corsair 4x2 GB RAM which I don't think is relevant but can't hurt to add. I'm also going to have drives which I don't think will consume all that much power. Thanks for the help.
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