what watt psu i need?

Solution
The GPU's max power is 250 Watts even with a overclock I would imagine 300 is probably a good range for the GPU. Then the CPU is 69 watts. Yea you are quite fine with your setup. I would however like to add that you do have a lot of fans within your setup. Hopefully you are purchasing premium fans. I personally would say that its best to go for semi modular because you are going to need the 24 pin and the 12v power for your motherboard. I have a AX850 and while I have individually sleeved cables and it is modular it does come at quite the premium and you may not want to stomach it.

http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-780/specifications
The GPU's max power is 250 Watts even with a overclock I would imagine 300 is probably a good range for the GPU. Then the CPU is 69 watts. Yea you are quite fine with your setup. I would however like to add that you do have a lot of fans within your setup. Hopefully you are purchasing premium fans. I personally would say that its best to go for semi modular because you are going to need the 24 pin and the 12v power for your motherboard. I have a AX850 and while I have individually sleeved cables and it is modular it does come at quite the premium and you may not want to stomach it.

http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-780/specifications
 
Solution