Offhand, I would think 600W PSU is big enough. HOWEVER, it has proven that having a much larger PSU than required just works better. It will use the wattage it needs with the remaining as reserve. Your GPU is requiring at least a PSU of 450W alone. You can't be too cheap when it comes to the PSU as it is the workhorse of the PC and not appreciated unitl it falters. Plus, if you OC or push the PC into any extremes and the heat build-up isn't cooled well enough will degenerate the PSU and the stable wattage levels drop forcing undesired results. I can leave saying, get the best you can afford and make the PSU the biggest hulking one beyond 600W. Many users are using 700W now. At least check the specs of your new build with the online calculator, it's not that hard to use, it's straight-forward Q&A's
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